Every Pro Baseball Player Charlie Has Seen: O
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
- Earl Oakes (pitcher, b. 1985, Connecticut)
- 2009: Midwest Sliders of Ypsilanti, Frontier League (independent) - 1 game 25-Jul
- Matt Oakes (catcher/first base, b. 1979, Oklahoma)
- 2004: Mid-Missouri Mavericks, Frontier League (independent) - 1 game 10-Jul
- Mike Oakland (first baseman, b. 1970)
- 1994: Central Valley Rockies, California League (High-A) - 1 game 3-Sep
- Matt Oakley (pitcher, b. 1973, United Kingdom)
- 1996: Jamestown Jammers, New York-Penn League (short-season) - 1 game 16-Aug
- Trevor Oaks (pitcher, b. 1993, California)
- 2019: Surprise Saguaros, Arizona Fall League - 1 game 16-Oct
- Johnny Oates (catcher, b. 1946, North Carolina; d. 2004, Virginia)
- 1980: New York Yankees, American League (MLB) - 1 game 2-Sep
- Kyle Obal (catcher, b. 1986)
- 2011: New York Federals, Can-Am League (independent) - 2 games 22-Jun 23-Jun
- Sherman Obando (outfielder, b. 1970, Panama)
- 1992: Albany-Colonie Yankees, Eastern League (AA) - 1 game 7-Aug
- 1994: Rochester Red Wings, International League (AAA) - 1 game 12-Aug
- 1996: Montreal Expos, National League (MLB) - 1 game 28-Jun
- Bailey Ober (pitcher, b. 1995, North Carolina)
- 2019: Fort Myers Miracle, Florida State League (High-A) - 1 game 13-Apr
- 2021: Minnesota Twins, Major League Baseball - 1 game 5-Jul
- Chad Oberacker (outfielder, b. 1989, Pennsylvania)
- 2011: Vermont Lake Monsters, New York-Penn League (short-season) - 1 game 31-Aug
- Scott Oberg (pitcher, b. 1990, Massachusetts)
- 2019: Colorado Rockies, Major League Baseball - 1 game 3-Apr
- Ken Oberkfell (infielder, b. 1956, Illinois)
- 1992: California Angels, American League (MLB) - 1 game 23-Aug
- Matt Oberste (first baseman, b. 1991, Arkansas)
- 2013: Brooklyn Cyclones, New York-Penn League (short-season) - 1 game 14-Aug
- 2017: Binghamton Rumble Ponies, Eastern League (AA) - 2 games 18-Aug g1 18-Aug g2
- 2018: Binghamton Rumble Ponies, Eastern League (AA) - 3 games 9-May 28-May 20-Jun
- Wilmer Oberto (first base/outfield, b. 1992, Venezuela)
- 2014: Lakewood BlueClaws, South Atlantic League (Low-A) - 1 game 23-Apr
- Norberto Obeso (outfielder, b. 1995, Mexico)
- Wirfin Obispo (pitcher, b. 1984, Dominican Republic)
- 2012: Pensacola Blue Wahoos, Southern League (AA) - 1 game 12-Aug
- Spencer Oborn (outfielder, b. 1977, California)
- 2000: Burlington Bees, Midwest League (Low-A) - 1 game 13-Aug
- Mark Obradovich (catcher, b. 1980, Alabama)
- 2001: Pittsfield Astros, New York-Penn League (short-season) - 2 games 19-Jul 21-Jul
- Mike Obradovich (pitcher, b. 1985, Alabama)
- 2008: Staten Island Yankees, New York-Penn League (short-season) - 1 game 5-Sep
- Omar Obregon (infielder, b. 1994, Nicaragua)
- 2017: Florida Fire Frogs, Florida State League (High-A) - 2 games 27-May 28-May
- 2018: Windy City ThunderBolts, Frontier League (independent) - 1 game 4-Aug
- 2021: Nicaragua, Americas Olympic Qualifier - 1 game 2-Jun
- Charlie O'Brien (catcher, b. 1960, Oklahoma)
- 1990: Milwaukee Brewers, American League (MLB) - 1 game 15-Aug
- 1990: New York Mets, National League (MLB) - 1 game 9-Sep
- 1992: New York Mets, National League (MLB) - 1 game 31-Aug g1
- 1993: New York Mets, National League (MLB) - 5 games 25-Jun 24-Aug 24-Sep 25-Sep 30-Sep
- 1996: Toronto Blue Jays, American League (MLB) - 1 game 8-Sep
- 1997: Toronto Blue Jays, American League (MLB) - 1 game 21-Sep
- Kevin O'Brien (first baseman, b. 1981, Massachusetts)
- 2001: Hudson Valley Renegades, New York-Penn League (short-season) - 2 games 25-Aug 26-Aug
- 2002: Hudson Valley Renegades, New York-Penn League (short-season) - 2 games 30-Jun 2-Sep
- Matt O'Brien (pitcher, b. 1977, Washington)
- 2004: Sacramento RiverCats, Pacific Coast League (AAA) - 1 game 9-Apr
- Mikey O'Brien (pitcher, b. 1990, Virginia)
- 2012: Trenton Thunder, Eastern League (AA) - 1 game 4-Jul
- 2013: Trenton Thunder, Eastern League (AA) - 1 game 5-Sep
- Peter O'Brien (catcher/first base, b. 1990, Florida)
- 2012: Staten Island Yankees, New York-Penn League (short-season) - 1 game 23-Aug
- 2014: Trenton Thunder, Eastern League (AA) - 1 game 27-Jul
- 2014: Salt River Rafters, Arizona Fall League - 2 games 8-Oct 10-Oct
- 2018: Miami Marlins, Major League Baseball - 2 games 12-Sep 30-Sep
- 2019: Miami Marlins, Major League Baseball - 1 game 1-Apr
- Riley O'Brien (pitcher, b. 1995)
- 2019: Montgomery Biscuits, Southern League (AA) - 1 game 29-May
- Tim O'Brien (infielder, b. 1983, California)
- 2006: Staten Island Yankees, New York-Penn League (short-season) - 2 games 18-Jul 28-Jul
- Wes O'Brien (pitcher, b. 1982, California)
- 2005: Lincoln Saltdogs, Northern League (independent) - 1 game 11-Aug
- Nate O'Bryan (pitcher, b. 1989)
- 2014: Traverse City Beach Bums, Frontier League (independent) - 1 game 27-Aug
- Carlos Ocampo (pitcher, b. 1998, Colombia)
- 2021: Colombia, Americas Olympic Qualifier - 1 game 1-Jun
- Sean Ochinko (catcher/infielder, b. 1987, Florida)
- 2011: Dunedin Blue Jays, Florida State League (High-A) - 1 game 10-Aug
- Alex Ochoa (outfielder, b. 1972, Florida)
- Blake Ochoa (catcher, b. 1985, Venezuela)
- 2007: Greensboro Grasshoppers, South Atlantic League (Low-A) - 1 game 5-Apr
- Ivan Ochoa (infielder, b. 1982, Venezuela)
- 2011: Chattanooga Lookouts, Southern League (AA) - 1 game 7-Aug
- Javier Ochoa (catcher, then pitcher, b. 1979, Venezuela)
- 2003: Capital City Bombers, South Atlantic League (Low-A) - 1 game 1-Aug
- Josh Ockimey (first baseman, b. 1995, Pennsylvania)
- 2015: Lowell Spinners, New York-Penn League (short-season) - 1 game 19-Aug
- 2017: Portland Sea Dogs, Eastern League (AA) - 2 games 18-Aug g1 18-Aug g2
- 2018: Portland Sea Dogs, Eastern League (AA) - 2 games 26-May g1 26-May g2
- 2018: Mesa Solar Sox, Arizona Fall League - 4 games 5-Nov 7-Nov 10-Nov 14-Nov
- 2021: Worcester Red Sox, Triple-A East - 1 game 7-Sep
- 2022: Lehigh Valley IronPigs, International League (AAA) - 2 games 16-Jul 24-Sep
- Justin O'Conner (catcher, b. 1992, Indiana)
- 2012: Hudson Valley Renegades, New York-Penn League (short-season) - 2 games 26-Aug 9-Sep
- 2014: Peoria Javelinas, Arizona Fall League - 2 games 9-Oct 10-Oct
- 2015: Montgomery Biscuits, Southern League (AA) - 2 games 25-Jul 28-Jul
- 2017: Durham Bulls, International League (AAA) - 1 game 19-Sep
- Brian O'Connor (pitcher, b. 1977, Ohio)
- 1996: Erie SeaWolves, New York-Penn League (short-season) - 1 game 14-Aug
- Brian O'Connor (catcher, b. 1977, Illinois)
- 2002: Greensboro Bats, South Atlantic League (Low-A) - 1 game 14-Jul
- Kevin O'Connor (first base/outfield, b. 1969)
- 1991: Durham Bulls, Carolina League (High-A) - 1 game 15-Aug
- McClain O'Connor (infielder, b. 1998, Utah)
- 2021: Missoula PaddleHeads, Pioneer League (independent) - 1 game 9-Jul
- Mike O'Connor (pitcher, b. 1980, Texas)
- 2011: Buffalo Bisons, International League (AAA) - 1 game 3-Jul
- Pablo O'Connor (outfielder, b. 1995, California)
- 2018: Auburn Doubledays, New York-Penn League (short-season) - 2 games 27-Jul 6-Sep
- Darren O'Day (pitcher, b. 1982, Florida)
- 2007: Arkansas Travelers, Texas League (AA) - 1 game 8-Aug
- 2014: Baltimore Orioles, Major League Baseball - 1 game 18-Apr
- 2015: Baltimore Orioles, Major League Baseball - 1 game 8-Sep
- 2017: Baltimore Orioles, Major League Baseball - 1 game 24-Sep
- 2019: Atlanta Braves, Major League Baseball - 1 game 29-Sep
- 2020: Atlanta Braves, Major League Baseball - 1 game 13-Oct
- 2021: New York Yankees, Major League Baseball - 2 games 11-Apr 14-Apr
- 2022: Gwinnett Stripers, International League (AAA) - 1 game 30-Aug
- Nick Oddo (catcher, b. 1992, California)
- 2022: Schaumburg Boomers, Frontier League (independent) - 1 game 5-Jul
- T.J. O'Donnell (infielder, b. 1970)
- 1992: Elmira Pioneers, New York-Penn League (short-season) - 1 game 9-Aug g2
- Joseph Odom (catcher, b. 1992, Alabama)
- 2019: Tacoma Rainiers, Pacific Coast League (AAA) - 1 game 2-Sep
- 2021: Durham Bulls, Triple-A East - 1 game 16-Jun
- Rouglas Odor (infielder, b. 1968, Venezuela)
- 1991: Canton-Akron Indians, Eastern League (AA) - 1 game 12-Aug
- 1993: Canton-Akron Indians, Eastern League (AA) - 1 game 9-Aug
- Rougned Odor (infielder, b. 1994, Venezuela)
- 2012: Hickory Crawdads, South Atlantic League (Low-A) - 1 game 11-Jul
- 2019: Texas Rangers, Major League Baseball - 2 games 17-Jul 19-Jul
- 2021: New York Yankees, Major League Baseball - 3 games 11-Apr 14-Apr 29-Jul
- 2022: Baltimore Orioles, Major League Baseball - 2 games 9-Apr 5-May
- Jake Odorizzi (pitcher, b. 1990, Illinois)
- 2013: Durham Bulls, International League (AAA) - 1 game 17-Sep
- 2014: Tampa Bay Rays, Major League Baseball - 1 game 10-Sep
- 2016: Tampa Bay Rays, Major League Baseball - 1 game 25-Aug
- 2017: Tampa Bay Rays, Major League Baseball - 1 game 11-Sep
- Chris O'Dowd (catcher, b. 1990, Ohio)
- 2013: Tri-City Dust Devils, Northwest League (short-season) - 1 game 22-Aug
- 2016: Birmingham Barons, Southern League (AA) - 1 game 2-Sep
- Randolph Oduber (outfielder, b. 1989, Aruba)
- 2014: Potomac Nationals, Carolina League (High-A) - 1 game 24-May
- 2019: Lincoln Saltdogs, American Association (independent) - 3 games 31-May 6-Jun 16-Jul
- Ross Oeder (infielder, b. 1985, Ohio)
- 2007: Batavia Muckdogs, New York-Penn League (short-season) - 1 game 4-Aug
- Jake Oester (infielder, b. 1986, Ohio)
- 2011: Winston-Salem Dash, Carolina League (High-A) - 1 game 28-May
- 2011: Birmingham Barons, Southern League (AA) - 1 game 11-Aug
- Todd Oetting (catcher, b. 1980, Missouri)
- 2003: Gateway Grizzlies, Frontier League (independent) - 1 game 29-Jul
- 2004: Gateway Grizzlies, Frontier League (independent) - 1 game 25-Jul
- Quentin Oexner (pitcher, b. 1990, New York)
- 2021: Wasco Reserve, Pecos League (independent) - 1 game 17-Jul
- Jose Offerman (infielder, b. 1968, Dominican Republic)
- 1993: Los Angeles Dodgers, National League (MLB) - 1 game 17-Aug
- 1999: Boston Red Sox, American League (MLB) - 2 games 24-Jul 19-Sep
- 2000: Boston Red Sox, Major League Baseball - 1 game 9-Jul
- 2003: Bridgeport Bluefish, Atlantic League (independent) - 1 game 3-Aug
- 2004: Minnesota Twins, Major League Baseball - 1 game 6-Oct
- 2005: New York Mets, Major League Baseball - 4 games 4-Jul 14-Sep 17-Sep 2-Oct
- Eric O'Flaherty (pitcher, b. 1985, Washington)
- 2010: Atlanta Braves, Major League Baseball - 1 game 19-Sep
- 2011: Atlanta Braves, Major League Baseball - 2 games 8-Sep g1 8-Sep g2
- 2012: Atlanta Braves, Major League Baseball - 2 games 8-Apr 13-Aug
- 2015: New York Mets, Major League Baseball - 1 game 20-Sep
- Gardner O'Flynn (pitcher, b. 1971, Massachusetts)
- 1994: Hudson Valley Renegades, New York-Penn League (short-season) - 2 games 19-Jun 26-Jul
- Cristofer Ogando (pitcher, b. 1993, Dominican Republic)
- 2019: Bowling Green Hot Rods, Midwest League (Low-A) - 1 game 30-May
- 2019: Charlotte Stone Crabs, Florida State League (High-A) - 1 game 20-Aug
- Emilio Ogando (pitcher, b. 1993, Florida)
- 2019: Northwest Arkansas Naturals, Texas League (AA) - 1 game 18-Jul
- Luis Ogando (infielder, b. 2003, Dominican Republic)
- Nefi Ogando (pitcher, b. 1989, Dominican Republic)
- 2014: Scottsdale Scorpions, Arizona Fall League - 1 game 9-Oct
- 2015: Reading Fightin Phils, Eastern League (AA) - 1 game 17-Jun
- Keshawn Ogans (infielder, b. 2001, California)
- 2023: Salt River Rafters, Arizona Fall League - 2 games 11-Oct 14-Oct
- Jamie Ogden (first base/outfield, b. 1972, Minnesota)
- 1993: Fort Myers Miracle, Florida State League (High-A) - 1 game 12-Aug
- Chad Ogea (pitcher, b. 1970, Louisiana)
- 1997: Buffalo Bisons, American Association (AAA) - 1 game 9-Aug g2
- Braeden Ogle (pitcher, b. 1997, Florida)
- 2019: Bradenton Marauders, Florida State League (High-A) - 1 game 9-Aug
- Rylie Ogle (pitcher, b. 1977, California)
- 2001: Brooklyn Cyclones, New York-Penn League (short-season) - 2 games 26-Aug 6-Sep
- 2002: Brooklyn Cyclones, New York-Penn League (short-season) - 1 game 30-Aug g2
- Luke Oglesby (outfielder, b. 1971, Colorado)
- 1995: Wilmington Blue Rocks, Carolina League (High-A) - 1 game 31-Aug
- Travis Oglesby (catcher/first base, b. 1977, California)
- 2004: North Shore Spirit, Northeast League (independent) - 1 game 16-Sep
- 2005: North Shore Spirit, Can-Am League (independent) - 2 games 25-Jun 23-Jul
- Brian O'Grady (outfielder, b. 1992, Pennsylvania)
- 2016: Daytona Tortugas, Florida State League (High-A) - 1 game 23-Aug g1
- 2016: Peoria Javelinas, Arizona Fall League - 1 game 12-Oct
- Chris O'Grady (pitcher, b. 1990, New York)
- 2015: Arkansas Travelers, Texas League (AA) - 1 game 30-Jul
- 2018: Miami Marlins, Major League Baseball - 1 game 30-Mar
- Dennis O'Grady (pitcher, b. 1989, New York)
- 2018: Long Island Ducks, Atlantic League (independent) - 1 game 23-Sep
- Alex Ogren (pitcher, b. 1995)
- 2019: Sioux Falls Canaries, American Association (independent) - 1 game 6-Jun
- Ryne Ogren (infielder, b. 1997, Pennsylvania)
- 2019: Delmarva Shorebirds, South Atlantic League (Low-A) - 1 game 30-Apr
- Jamal O'Guinn (outfielder, b. 1999, California)
- Faustino Oguisten (infielder, b. 1991, Dominican Republic)
- 2014: Great Lakes Loons, Midwest League (Low-A) - 1 game 28-Aug
- Seung-hwan Oh (pitcher, b. 1982, South Korea)
- 2016: St. Louis Cardinals, Major League Baseball - 1 game 27-Jul
- Connor O'Halloran (pitcher, b. 2002, Ontario)
- 2023: Dunedin Blue Jays, Florida State League (Low-A) - 1 game 18-Aug
- Greg O'Halloran (catcher/first base, b. 1968, Ontario)
- 1994: Portland Sea Dogs, Eastern League (AA) - 1 game 20-Aug
- Sean O'Hare (infielder, b. 1991, New Jersey)
- 2013: Newark Bears, Can-Am League (independent) - 3 games 5-Aug 9-Aug 15-Aug
- 2014: Rockland Boulders, Can-Am League (independent) - 1 game 1-Aug
- Rafael Ohashi (pitcher, b. 2002, Brazil)
- 2021: Dunedin Blue Jays, Low-A Southeast - 3 games 9-May 16-May 5-Jun
- 2022: Dunedin Blue Jays, Florida State League (Low-A) - 3 games 4-Jun 11-Jun 9-Sep
- 2023: Dunedin Blue Jays, Florida State League (Low-A) - 2 games 31-May 20-Aug
- Ryan O'Hearn (first base/outfield, b. 1993, Texas)
- 2016: Surprise Saguaros, Arizona Fall League - 2 games 11-Oct 13-Oct
- 2019: Kansas City Royals, Major League Baseball - 1 game 24-Apr
- 2019: Omaha Storm Chasers, Pacific Coast League (AAA) - 1 game 23-Jul
- 2021: Kansas City Royals, Major League Baseball - 1 game
- 2022: Kansas City Royals, Major League Baseball - 1 game 21-Aug
- 2024: Baltimore Orioles, Major League Baseball - 5 games 7-Jun 8-Jun 9-Jun 10-Jun 18-Sep
- Tomo Ohka (pitcher, b. 1976, Japan)
- 2000: Pawtucket Red Sox, International League (AAA) - 1 game 8-Jul
- 2003: Montreal Expos, Major League Baseball - 1 game 6-Sep
- Pierson Ohl (pitcher, b. 1999, California)
- Ross Ohlendorf (pitcher, b. 1982, Texas)
- 2007: Scranton/Wilkes-Barre Yankees, International League (AAA) - 1 game 28-Aug
- 2007: New York Yankees, Major League Baseball - 2 games 22-Sep 30-Sep
- 2015: Texas Rangers, Major League Baseball - 1 game 22-May
- Mike Ohlman (catcher, b. 1990, Florida)
- 2012: Delmarva Shorebirds, South Atlantic League (Low-A) - 1 game 21-Aug
- 2014: Glendale Desert Dogs, Arizona Fall League - 1 game 9-Oct
- 2018: Pawtucket Red Sox, International League (AAA) - 1 game 31-Jul
- Liam Ohlmann (pitcher, b. 1986, Connecticut)
- 2009: Wisconsin Timber Rattlers, Midwest League (Low-A) - 1 game 28-Jul
- 2010: Florence Freedom, Frontier League (independent) - 1 game 3-Sep
- Will Ohman (pitcher, b. 1977, Germany)
- 2009: Albuquerque Isotopes, Pacific Coast League (AAA) - 1 game 24-Aug
- 2010: Florida Marlins, Major League Baseball - 1 game 6-Sep day
- Kevin Ohme (pitcher, b. 1971, Florida)
- 1996: Hardware City Rock Cats, Eastern League (AA) - 2 games 15-Jun 25-Aug
- Logan O'Hoppe (catcher, b. 2000, New York)
- 2021: Peoria Javelinas, Arizona Fall League - 2 games 16-Oct 20-Oct
- 2023: Los Angeles Angels, Major League Baseball - 1 game 21-Sep
- 2024: Los Angeles Angels, Major League Baseball - 3 games 16-Apr 17-Apr 18-Apr
- Shohei Ohtani (pitcher, b. 1994, Japan)
- 2018: Los Angeles Angels, Major League Baseball - 1 game 11-Aug
- 2021: Los Angeles Angels, Major League Baseball - 4 games 10-Apr 27-Jun 11-Jul 18-Jul
- 2022: Los Angeles Angels, Major League Baseball - 2 games 22-Aug 25-Aug
- Kirt Ojala (pitcher, b. 1968, Michigan)
- 1992: Albany-Colonie Yankees, Eastern League (AA) - 1 game 7-Aug
- Augie Ojeda (infielder, b. 1974, California)
- 2001: Chicago Cubs, Major League Baseball - 1 game 29-Jul
- 2008: Arizona Diamondbacks, Major League Baseball - 1 game 28-Jul
- Bob Ojeda (pitcher, b. 1957, California)
- 1993: Cleveland Indians, American League (MLB) - 1 game 3-Sep
- Erick Ojeda (pitcher, b. 1975, Venezuela)
- 1998: Atlantic City Surf, Atlantic League (independent) - 1 game 4-Jul
- Jose Ojeda (pitcher, b. 2005, Venezuela)
- 2024: FCL Braves, Florida Complex League (rookie) - 1 game 22-Jun
- Luis Ojeda (pitcher, b. 1997, Venezuela)
- 2019: GCL Yankees East, Gulf Coast League (rookie) - 1 game 31-Jul g2
- Miguel Ojeda (catcher, b. 1975, Mexico)
- 2003: San Diego Padres, Major League Baseball - 1 game 2-Aug g2
- 2004: San Diego Padres, Major League Baseball - 1 game 8-Aug
- Brian O'Keefe (pitcher, b. 1992, New York)
- 2016: Washington Wild Things, Frontier League (independent) - 1 game 3-Jul
- Brian O'Keefe (catcher, b. 1993, New York)
- 2014: State College Spikes, New York-Penn League (short-season) - 2 games 2-Aug 15-Aug
- 2015: Peoria Chiefs, Midwest League (Low-A) - 1 game 4-Sep
- Mike O'Keefe (first base/outfield, b. 1978, Connecticut)
- 2000: Cedar Rapids Kernels, Midwest League (Low-A) - 1 game 13-Aug
- 2004: Portland Sea Dogs, Eastern League (AA) - 1 game 1-Aug
- 2005: New Haven County Cutters, Can-Am League (independent) - 2 games 25-Jun 3-Jul
- Steven Okert (pitcher, b. 1991, California)
- 2014: Scottsdale Scorpions, Arizona Fall League - 1 game 9-Oct
- 2017: Sacramento RiverCats, Pacific Coast League (AAA) - 1 game 30-Jul
- 2018: Sacramento RiverCats, Pacific Coast League (AAA) - 1 game 15-Aug
- 2019: Sacramento RiverCats, Pacific Coast League (AAA) - 1 game 17-Sep
- 2021: Miami Marlins, Major League Baseball - 1 game 26-Sep
- 2022: Miami Marlins, Major League Baseball - 1 game 16-Apr
- 2023: Jacksonville Jumbo Shrimp, International League (AAA) - 1 game 19-Apr
- 2023: Miami Marlins, Major League Baseball - 3 games 25-Jul 29-Aug 29-Sep
- Jefferson Olacio (pitcher, b. 1994, Dominican Republic)
- 2013: Kannapolis Intimidators, South Atlantic League (Low-A) - 1 game 25-May
- 2014: Glendale Desert Dogs, Arizona Fall League - 1 game 9-Oct
- Bob Olah (first baseman, b. 1968)
- 1987: Little Falls Mets, New York-Penn League (short-season) - 1 game 13-Aug
- Adam Olbrychowski (pitcher, b. 1986, California)
- 2008: Charleston RiverDogs, South Atlantic League (Low-A) - 1 game 18-Aug
- 2010: Trenton Thunder, Eastern League (AA) - 1 game 5-Sep
- 2012: Potomac Nationals, Carolina League (High-A) - 1 game 8-Aug
- Jon Olczak (pitcher, b. 1993, North Carolina)
- Jon Olczak (pitcher, b. 1993, North Carolina)
- 2019: San Antonio Missions, Pacific Coast League (AAA) - 1 game 15-Jul
- 2019: Biloxi Shuckers, Southern League (AA) - 1 game 11-Sep
- Quintin Oldenburg (pitcher, b. 1978)
- 2005: Calgary Vipers, Northern League (independent) - 1 game 12-Aug
- Rob Oldham (pitcher, b. 1974)
- 1994: Burlington Indians, Appalachian League (rookie) - 1 game 3-Jul
- Taylor Oldham (infielder, b. 1989, Florida)
- 2016: Florence Freedom, Frontier League (independent) - 1 game 3-Jul
- 2018: Trois-Rivieres Aigles, Can-Am League (independent) - 1 game 18-Jul day
- 2021: Florence Y'alls, Frontier League (independent) - 1 game 7-Aug
- Troy O'Leary (outfielder, b. 1969, California)
- 1990: Beloit Brewers, Midwest League (Low-A) - 1 game 14-Aug
- 1996: Boston Red Sox, American League (MLB) - 2 games 3-Aug day 22-Sep
- 1997: Boston Red Sox, American League (MLB) - 3 games 27-Jul 16-Sep g1 16-Sep g2
- 1998: Boston Red Sox, American League (MLB) - 2 games 11-Jul 26-Jul
- 1999: Boston Red Sox, American League (MLB) - 2 games 24-Jul 19-Sep
- 2000: Boston Red Sox, Major League Baseball - 1 game 9-Jul
- John Olerud (first baseman, b. 1968, Washington)
- Mikeson Oliberto (outfielder, b. 1990, Dominican Republic)
- 2014: Charleston RiverDogs, South Atlantic League (Low-A) - 1 game 23-Apr
- Kaliko Oligo (outfielder, b. 1981)
- 2005: Ohio Valley Redcoats, Frontier League (independent) - 1 game 20-Aug
- Durin O'Linger (pitcher, b. 1993, Florida)
- 2017: Lowell Spinners, New York-Penn League (short-season) - 1 game 22-Jul
- Chad Oliva (outfielder, b. 1980, New York)
- 2003: Lakewood BlueClaws, South Atlantic League (Low-A) - 1 game 6-May
- Jared Oliva (outfielder, b. 1995, California)
- 2019: Peoria Javelinas, Arizona Fall League - 3 games 16-Oct 18-Oct 19-Oct
- 2021: Pittsburgh Pirates, Major League Baseball - 1 game 19-Jul
- 2022: Indianpolis Indians, International League (AAA) - 1 game 26-Jun
- 2023: Salt Lake Bees, Pacific Coast League (AAA) - 1 game 8-Aug
- Jose Oliva (infielder, b. 1971, Dominican Republic)
- 1993: Richmond Braves, International League (AAA) - 1 game 4-Sep
- Ricardo Olivar (catcher/outfielder, b. 2001, Venezuela)
- Edward Olivares (outfielder, b. 1996, Venezuela)
- 2018: Lake Elsinore Storm, California League (High-A) - 2 games 10-Aug 17-Aug
- 2019: Amarillo Sod Poodles, Texas League (AA) - 2 games 20-Jul 25-Jul
- 2021: Kansas City Royals, Major League Baseball - 1 game 16-Sep
- Gerardo Olivares (catcher, then pitcher, b. 1988, Dominican Republic)
- 2011: Hudson Valley Renegades, New York-Penn League (short-season) - 1 game 18-Aug
- Helcris Olivarez (pitcher, b. 2000, Dominican Republic)
- 2021: Spokane Indians, High-A West - 1 game 13-Jul
- Jose Olivares (pitcher, b. 2003, Venezuela)
- 2023: Fort Myers Mighty Mussels, Florida State League (Low-A) - 2 games 15-Apr 2-Sep
- Miguel Olivares (pitcher, b. 2003, Venezuela)
- 2023: FCL Twins, Florida Complex League (rookie) - 1 game 21-Aug
- Omar Olivares (pitcher, b. 1967, Puerto Rico)
- 1992: St. Louis Cardinals, National League (MLB) - 1 game 18-Aug
- 1993: St. Louis Cardinals, National League (MLB) - 1 game 25-Jun
- 1997: Detroit Tigers, American League (MLB) - 1 game 4-Jul g2
- 1997: Seattle Mariners, American League (MLB) - 1 game 3-Sep
- Pablo Olivares (outfielder, b. 1998, Venezuela)
- Teuris Olivares (infielder, b. 1978, Dominican Republic)
- 2001: Norwich Navigators, Eastern League (AA) - 1 game 29-Apr
- 2004: Trenton Thunder, Eastern League (AA) - 2 games 3-Aug g2 4-Sep
- 2005: Newark Bears, Atlantic League (independent) - 2 games 24-Jun 10-Jul
- 2006: Road Warriors, Atlantic League (independent) - 1 game 16-Sep
- 2007: Somerset Patriots, Atlantic League (independent) - 5 games 21-Jul 3-Aug 21-Sep 23-Sep 24-Sep
- 2008: Somerset Patriots, Atlantic League (independent) - 5 games 20-Jul 14-Sep 18-Sep 24-Sep 28-Sep
- 2009: Somerset Patriots, Atlantic League (independent) - 4 games 16-Jul 30-Aug 25-Sep 27-Sep
- 2010: Camden Riversharks, Atlantic League (independent) - 1 game 15-Aug
- Martin Olivas (infielder, then pitcher, b. 2001, Mexico)
- 2019: GCL Tigers East, Gulf Coast League (rookie) - 2 games 10-Aug 19-Aug
- 2022: FCL Tigers, Florida Complex League (rookie) - 1 game 10-Jun
- Russ Olive (first baseman, b. 1996, Massachusetts)
- 2019: Charlotte Stone Crabs, Florida State League (High-A) - 1 game 10-Apr
- Joe Oliveira (catcher, b. 1987, California)
- 2012: Frederick Keys, Carolina League (High-A) - 1 game 3-Sep
- Al Oliver (first base/outfield, b. 1946, Ohio)
- 1984: Philadelphia Phillies, National League (MLB) - 1 game 26-Sep
- Andre Oliver (utility, b. 1990)
- 2014: Raton Osos, Pecos League (independent) - 1 game 22-Jul
- Andy Oliver (pitcher, b. 1987, Ohio)
- 2016: Norfolk Tides, International League (AAA) - 2 games 30-May 21-Aug
- Chris Oliver (pitcher, b. 1993, Texas)
- 2014: Williamsport Crosscutters, New York-Penn League (short-season) - 1 game 4-Jul g2
- 2015: Kane County Cougars, Midwest League (Low-A) - 2 games 29-Aug g2 3-Sep
- Connor Oliver (outfielder, b. 1993, California)
- 2015: Carolina Mudcats, Carolina League (High-A) - 1 game 23-May
- Connor Oliver (pitcher, b. 2001, Illinois)
- Darren Oliver (pitcher, b. 1970, Missouri)
- 2006: New York Mets, Major League Baseball - 1 game 16-Apr
- Jared Oliver (pitcher, b. 1993, Georgia)
- 2017: Lowell Spinners, New York-Penn League (short-season) - 1 game 22-Jul
- Joe Oliver (catcher, b. 1965, Tennessee)
- 1993: Cincinnati Reds, National League (MLB) - 2 games 18-Aug 24-Aug
- 1995: Milwaukee Brewers, American League (MLB) - 1 game 16-Aug
- 1997: Cincinnati Reds, National League (MLB) - 1 game 25-Aug day
- 2001: Pawtucket Red Sox, International League (AAA) - 1 game 13-Jul
- Will Oliver (pitcher, b. 1987, California)
- 2015: Somerset Patriots, Atlantic League (independent) - 1 game 26-Sep
- 2016: Somerset Patriots, Atlantic League (independent) - 2 games 31-Jul g1 6-Sep
- 2017: Somerset Patriots, Atlantic League (independent) - 1 game 22-Sep
- Hector Olivera (infielder, b. 1985, Cuba)
- 2015: Atlanta Braves, Major League Baseball - 1 game 23-Sep
- Orlando Olivera (outfielder, b. 1990, Florida)
- 2016: Palm Beach Cardinals, Florida State League (High-A) - 1 game 26-Aug
- Rafael Oliveras (infielder, b. 1995, Puerto Rico)
- 2016: GCL Red Sox, Gulf Coast League (rookie) - 1 game 27-Aug
- Leonardo Oliveros (catcher, b. 1975, Venezuela)
- 1996: Batavia Clippers, New York-Penn League (short-season) - 1 game 16-Aug
- Lester Oliveros (pitcher, b. 1988, Venezuela)
- 2011: Minnesota Twins, Major League Baseball - 1 game 19-Sep
- Luis Oliveros (catcher, b. 1983, Venezuela)
- 2005: San Antonio Missions, Texas League (AA) - 1 game 4-Sep
- Rayner Oliveros (pitcher, b. 1985, Venezuela)
- 2011: Quebec Les Capitales, Can-Am League (independent) - 1 game 2-Aug
- Carlos Olivo (pitcher, b. 1979, Dominican Republic)
- 2000: Johnson City Cardinals, Appalachian League (rookie) - 1 game 2-Aug
- Miguel Olivo (catcher, b. 1978, Dominican Republic)
- 2009: Kansas City Royals, Major League Baseball - 1 game 28-Sep
- Ricardo Olivo (catcher, b. 1990, Dominican Republic)
- 2017: Dominican Republic, Can-Am League (independent) - 1 game 14-Jun
- Adam Oller (pitcher, b. 1994, Texas)
- 2022: Oakland Athletics, Major League Baseball - 1 game 12-Apr
- Manny Olloque (utility, b. 1996, California)
- 2017: Lexington Legends, South Atlantic League (Low-A) - 1 game 30-Aug g2
- 2018: Lexington Legends, South Atlantic League (Low-A) - 1 game 13-Sep
- Jose Olmeda (infielder, b. 1968, Puerto Rico)
- 1996: Charlotte Knights, International League (AAA) - 1 game 31-Aug
- 2000: Atlantic City Surf, Atlantic League (independent) - 2 games 3-Jul 7-Aug
- Jose Olmeda (infielder, b. 1977, Puerto Rico)
- Ray (Rainer) Olmedo (infielder, b. 1981, Venezuela)
- 2000: Dayton Dragons, Midwest League (Low-A) - 1 game 21-Jul
- 2003: Cincinnati Reds, Major League Baseball - 2 games 3-Jul 4-Jul
- 2007: Toronto Blue Jays, Major League Baseball - 1 game 22-Sep
- 2008: Columbus Clippers, International League (AAA) - 1 game 30-Aug
- 2009: Durham Bulls, International League (AAA) - 1 game 17-Sep
- 2011: Durham Bulls, International League (AAA) - 1 game 5-Aug
- David Olmedo-Barrera (outfielder, b. 1994, California)
- 2019: Chicago Dogs, American Association (independent) - 1 game 1-Jun
- Edgar Olmos (pitcher, b. 1990, California)
- 2016: Norfolk Tides, International League (AAA) - 1 game 21-Aug
- Michael Olmsted (pitcher, b. 1987, California)
- 2013: Nashville Sounds, Pacific Coast League (AAA) - 1 game 23-Jul
- Johnny Olmstead (infielder, b. 2000, California)
- Walter Olmstead (utility, b. 1980, Texas)
- 2002: Billings Mustangs, Pioneer League (rookie) - 1 game 6-Aug
- 2007: El Paso Diablos, American Association (independent) - 1 game 12-Aug
- Adam Olow (outfielder, b. 1977)
- 2002: Dubois County Dragons, Frontier League (independent) - 1 game 28-Jul
- 2003: St. Paul Saints, Northern League (independent) - 1 game 27-Jul
- D.C. Olsen (catcher/first base, b. 1972, Utah)
- 1998: New Jersey Jackals, Northeast League (independent) - 3 games 3-Jul 19-Jul 22-Jul
- 1999: New Jersey Jackals, Northeast League (independent) - 1 game 18-Jun
- Kevin Olsen (pitcher, b. 1976, California)
- 1999: Kane County Cougars, Midwest League (Low-A) - 1 game 5-Sep
- 2003: Jupiter Hammerheads, Florida State League (High-A) - 1 game 29-Aug
- Mario Olsen (pitcher, b. 1973)
- 1998: Somerset Patriots, Atlantic League (independent) - 1 game 12-Jul
- Brian Olson (catcher/first base, b. 1993, Washington)
- 2019: Fargo-Moorhead RedHawks, American Association (independent) - 1 game 7-Jun
- Dan Olson (outfielder, b. 1975, New Jersey)
- 1997: Hickory Crawdads, South Atlantic League (Low-A) - 1 game 15-Aug
- 1999: Winston-Salem Warthogs, Carolina League (High-A) - 1 game 8-Aug
- Garrett Olson (pitcher, b. 1983, California)
- 2005: Aberdeen IronBirds, New York-Penn League (short-season) - 1 game 17-Jul
- Greg Olson (catcher, b. 1960, Minnesota)
- 1988: Tidewater Tides, International League (AAA) - 1 game 29-Jul
- 1991: Atlanta Braves, National League (MLB) - 1 game 6-Sep
- 1992: Atlanta Braves, National League (MLB) - 1 game 31-Aug g1
- Gregg Olson (pitcher, b. 1966, Nebraska)
- 1991: Baltimore Orioles, American League (MLB) - 1 game 15-Sep
- J.B. Olson (pitcher, b. 1995, Texas)
- 2022: Charlotte Knights, International League (AAA) - 1 game 16-Jul
- Jason Olson (pitcher, b. 1978, Arizona)
- 2007: York Revolution, Atlantic League (independent) - 1 game 21-Jul
- 2008: York Revolution, Atlantic League (independent) - 1 game 20-Sep
- Matt Olson (infielder, b. 1994, Georgia)
- 2014: Mesa Solar Sox, Arizona Fall League - 1 game 10-Oct
- 2018: Oakland Athletics, Major League Baseball - 1 game 11-Aug
- 2021: Oakland Athletics, Major League Baseball - 1 game 16-Sep
- 2022: Atlanta Braves, Major League Baseball - 5 games 3-May g1 3-May g2 15-Aug 25-Sep 26-Sep
- 2023: Atlanta Braves, Major League Baseball - 1 game 7-Jun
- 2024: Atlanta Braves, Major League Baseball - 1 game 17-Jun
- Reese Olson (pitcher, b. 1999, Georgia)
- 2022: Erie SeaWolves, Eastern League (AA) - 1 game 24-Jun
- 2024: Detroit Tigers, Major League Baseball - 2 games 17-Jun 26-Sep
- Ryan Olson (pitcher, b. 1980, California)
- 2003: Capital City Bombers, South Atlantic League (Low-A) - 1 game 1-Aug
- Ryan Olson (pitcher, b. 1994, California)
- 2019: Daytona Tortugas, Florida State League (High-A) - 1 game 14-Apr
- Tyler Olson (pitcher, b. 1989, Washington)
- 2018: Cleveland Indians, Major League Baseball - 1 game 20-Sep
- Eric Olszewski (pitcher, b. 1974, Texas)
- 2000: Aberdeen Arsenal, Atlantic League (independent) - 1 game 6-Jul
- Eddie Olszta (catcher/outfielder, b. 1979, Illinois)
- 2003: Joliet Jackhammers, Northern League (independent) - 1 game 27-Jul
- Mike Olt (infielder, b. 1988, Connecticut)
- 2013: Iowa Cubs, Pacific Coast League (AAA) - 1 game 29-Aug
- 2017: Portland Sea Dogs, Eastern League (AA) - 1 game 18-Aug g2
- 2018: Pawtucket Red Sox, International League (AAA) - 1 game 27-May
- John Omahen (pitcher, b. 1989, California)
- 2015: Mobile BayBears, Southern League (AA) - 1 game 26-Jul
- Shawn O'Malley (infielder, b. 1987, Washington)
- 2017: Tacoma Rainiers, Pacific Coast League (AAA) - 1 game 6-Aug
- Tom O'Malley (infielder, b. 1960, New Jersey)
- 1990: New York Mets, National League (MLB) - 1 game 9-Sep
- Diego Omana (catcher, b. 2003, Venezuela)
- Brian Omogrosso (pitcher, b. 1984, Pennsylvania)
- 2011: Birmingham Barons, Southern League (AA) - 1 game 29-May
- Isaac Omura (infielder, b. 1984, Hawaii)
- 2006: Kane County Cougars, Midwest League (Low-A) - 1 game 7-Aug
- Jorge Ona (outfielder, b. 1996, Cuba)
- Logan Ondrusek (pitcher, b. 1985, Texas)
- 2011: Cincinnati Reds, Major League Baseball - 1 game 26-Sep
- 2013: Cincinnati Reds, Major League Baseball - 1 game 17-Aug
- 2018: Long Island Ducks, Atlantic League (independent) - 1 game 4-Sep
- Conner O'Neil (pitcher, b. 1994, Washington)
- 2019: St. Lucie Mets, Florida State League (High-A) - 1 game 15-Apr
- Dan O'Neill (pitcher, b. 1964)
- 1990: New Britain Red Sox, Eastern League (AA) - 1 game 11-Aug
- Dan O'Neill (outfielder, b. 1976, Illinois)
- 1999: Batavia Muckdogs, New York-Penn League (short-season) - 1 game 28-Aug
- Matt O'Neill (catcher, b. 1997, New Jersey)
- 2021: St. Lucie Mets, Low-A Southeast - 1 game 14-Aug g1
- 2022: Brooklyn Cyclones, South Atlantic League (High-A) - 2 games 8-May g1 8-May g2
- Michael O'Neill (outfielder, b. 1988, California)
- Michael O'Neill (outfielder, b. 1992, Ohio)
- 2013: Staten Island Yankees, New York-Penn League (short-season) - 1 game 6-Aug
- 2014: Charleston RiverDogs, South Atlantic League (Low-A) - 1 game 23-Apr
- 2016: Trenton Thunder, Eastern League (AA) - 2 games 2-Aug 20-Aug
- 2019: Chattanooga Lookouts, Southern League (AA) - 1 game 15-Aug
- Paul O'Neill (outfielder, b. 1963, Ohio)
- Tyler O'Neill (outfielder, b. 1995, British Columbia)
- 2016: Peoria Javelinas, Arizona Fall League - 3 games 11-Oct 12-Oct 14-Oct
- 2017: Memphis Redbirds, Pacific Coast League (AAA) - 2 games 6-Aug 19-Sep
- 2018: St. Louis Cardinals, Major League Baseball - 1 game 20-Aug
- 2021: St. Louis Cardinals, Major League Baseball - 1 game 17-Sep
- 2022: St. Louis Cardinals, Major League Baseball - 3 games 7-Jun 8-Jun 9-Jun
- 2024: Boston Red Sox, Major League Baseball - 1 game 20-May
- Emilio Ontiveros (infielder, b. 1985, Venezuela)
- 2007: Greensboro Grasshoppers, South Atlantic League (Low-A) - 1 game 5-Apr
- Jeff Ontiveros (catcher/first base, b. 1979, Texas)
- 2002: Lowell Spinners, New York-Penn League (short-season) - 2 games 4-Jul 6-Jul
- Steve Ontiveros (infielder, b. 1951, California)
- 1977: Chicago Cubs, National League (MLB) - 1 game 12-Jul
- Ben Onyshko (pitcher, b. 1996, Manitoba)
- 2021: Canada, Americas Olympic Qualifier - 1 game 31-May
- Kevin Ool (pitcher, b. 1981, New York)
- 2006: Springfield Cardinals, Texas League (AA) - 1 game 3-Sep
- Ryan Opatkiewicz (infielder, b. 1974)
- 1994: Huntington Cubs, Appalachian League (rookie) - 1 game 3-Jul
- Shane Opitz (infielder, b. 1992, Colorado)
- 2019: High Point Rockers, Atlantic League (independent) - 1 game 3-May
- Cam Opp (pitcher, b. 1995, Colorado)
- 2022: Brooklyn Cyclones, South Atlantic League (High-A) - 1 game 8-May g2
* Ian Oquendo - see Ian Snell
- Johzan Oquendo (pitcher, b. 2001, Puerto Rico)
- 2022: Carolina Gigantes, Liga Clemente (winter) - 1 game 2-Dec
- Jose Oquendo (infielder, b. 1963, Puerto Rico)
- 1984: New York Mets, National League (MLB) - 1 game 17-Apr
- 1990: St. Louis Cardinals, National League (MLB) - 1 game 12-Aug
- James O'Quinn (pitcher, b. 1973, Florida)
- 1996: Cedar Rapids Kernels, Midwest League (Low-A) - 1 game 13-Aug
- Mickey O'Quinn (pitcher, b. 1978, Florida)
- 2005: Florence Freedom, Frontier League (independent) - 1 game 29-Jul
- Luis Ordaz (infielder, b. 1975, Venezuela)
- 2000: Kansas City Royals, Major League Baseball - 1 game 22-Jul day
- 2005: Durham Bulls, International League (AAA) - 1 game 28-Aug
- 2010: Syracuse Chiefs, International League (AAA) - 1 game 30-Jul
- Ernny Ordonez (first baseman, b. 1999, New York)
- Magglio Ordonez (outfielder, b. 1974, Venezuela)
- 1999: Chicago White Sox, American League (MLB) - 2 games 31-Jul 22-Sep
- 2009: Detroit Tigers, Major League Baseball - 3 games 26-Jul 26-Aug 6-Sep
- 2011: Detroit Tigers, Major League Baseball - 1 game 30-Sep
- Rey Ordonez (infielder, b. 1971, Cuba)
- Eric Ordorica (infielder, b. 1980, California)
- 2002: Jamestown Jammers, New York-Penn League (short-season) - 1 game 30-Jun
- John O'Reilly (pitcher, b. 1995, New Jersey)
- 2023: Indianapolis Indians, International League (AAA) - 1 game 1-Jul
- Ryan O'Reilly (pitcher, b. 1998, Illinois)
- 2022: Evansville Otters, Frontier League (independent) - 1 game 5-Jul
- Douglas Orellana (pitcher, b. 2002, Venezuela)
- Josnaider Orellana (catcher, b. 2004, Venezuela)
- 2024: FCL Braves, Florida Complex League (rookie) - 2 games 7-May 3-Jun
- Brennan Orf (first base/outfield, b. 2001, Missouri)
- Nate Orf (infielder, b. 1990, Missouri)
- 2013: Helena Brewers, Pioneer League (rookie) - 1 game 27-Aug
- 2019: San Antonio Missions, Pacific Coast League (AAA) - 2 games 15-Jul 21-Jul
- Mark Ori (first baseman, b. 1983, Illinois)
- 2006: Lexington Legends, South Atlantic League (Low-A) - 1 game 6-Sep
- Kevin Orie (infielder, b. 1972, Pennsylvania)
- 1998: Florida Marlins, National League (MLB) - 1 game 18-Sep
- 2001: Scranton/Wilkes-Barre Red Barons, International League (AAA) - 2 games 8-Jul 13-Jul
- Demi Orimoloye (outfielder, b. 1997, Nigeria)
- Robert (R.C.) Orlan (pitcher, b. 1990, Virginia)
- 2014: Auburn Doubledays, New York-Penn League (short-season) - 1 game 29-Aug
- 2016: Potomac Nationals, Carolina League (High-A) - 1 game 28-May
- Paulo Orlando (outfielder, b. 1985, Brazil)
- 2013: Omaha Storm Chasers, Pacific Coast League (AAA) - 1 game 17-Sep
- 2015: Kansas City Royals, Major League Baseball - 1 game 31-Oct
- 2018: Omaha Storm Chasers, Pacific Coast League (AAA) - 1 game 7-Aug
- Ben Orloff (infielder, b. 1987, California)
- 2010: Tri-City ValleyCats, New York-Penn League (short-season) - 1 game 14-Sep
- 2011: Lexington Legends, South Atlantic League (Low-A) - 1 game 2-Jul
- Joe Orloski (pitcher, b. 1979, Nevada)
- 2000: Queens Kings, New York-Penn League (short-season) - 1 game 9-Sep
- 2005: New Jersey Jackals, Can-Am League (independent) - 1 game 31-Aug
- 2006: New Jersey Jackals, Can-Am League (independent) - 1 game 14-Aug
- Rodney Ormond (pitcher, b. 1977, North Carolina)
- 1999: Delmarva Shorebirds, South Atlantic League (Low-A) - 1 game 10-Aug
- Dave Orndorff (utility, b. 1977, Pennsylvania)
- 1998: Fort Wayne Wizards, Midwest League (Low-A) - 1 game 15-Aug
- Jonathan Ornelas (infielder, b. 2000, Arizona)
- 2019: Hickory Crawdads, South Atlantic League (Low-A) - 2 games 30-Apr 11-Aug
- 2023: Texas Rangers, Major League Baseball - 1 game 7-Aug
- Tirso Ornelas (outfielder, b. 2000, Mexico)
- 2021: Fort Wayne TinCaps, High-A Central - 1 game 18-Sep
- 2022: Peoria Javelinas, Arizona Fall League - 2 games 12-Oct 13-Oct
- Eddie Oropesa (pitcher, b. 1971, Cuba)
- 1998: Shreveport Captains, Texas League (AA) - 1 game 25-Aug
- 2000: Shreveport Captains, Texas League (AA) - 1 game 20-Aug
- 2001: Scranton/Wilkes-Barre Red Barons, International League (AAA) - 1 game 13-Jul
- 2004: Portland Beavers, Pacific Coast League (AAA) - 1 game 20-Aug
- Asdrubal Oropeza (infielder, b. 1980, Venezuela)
- 1999: Jamestown Jammers, New York-Penn League (short-season) - 1 game 30-Jul
- 2003: Quebec Les Capitales, Northeast League (independent) - 3 games 28-Jun 6-Aug g1 6-Aug g2
- Willie Oropeza (catcher/infield, b. 1975, Venezuela)
- 1999: Massachusetts Mad Dogs, Northeast League (independent) - 1 game 17-Jul
- Jesse Orosco (pitcher, b. 1957, California)
- 1985: New York Mets, National League (MLB) - 1 game 9-Apr
- 1986: New York Mets, National League (MLB) - 1 game 14-Apr
- 1992: Milwaukee Brewers, American League (MLB) - 1 game 14-Aug g1
- 1996: Baltimore Orioles, American League (MLB) - 2 games 13-Jul g2 18-Sep
- 1997: Baltimore Orioles, American League (MLB) - 1 game 4-Jul g2
- 1998: Baltimore Orioles, American League (MLB) - 1 game 11-Jul
- Dernier Orozco (pitcher, b. 1982, Venezuela)
- 2003: GCL Red Sox, Gulf Coast League (rookie) - 1 game 25-Aug
- Eddie Orozco (pitcher, b. 1989, California)
- 2013: Boise Hawks, Northwest League (short-season) - 1 game 24-Aug
- Jio Orozco (pitcher, b. 1997, Arizona)
- 2017: Staten Island Yankees, New York-Penn League (short-season) - 1 game 9-Aug
- Rodrigo Orozco (outfielder, b. 1995, Panama)
- 2019: Amarillo Sod Poodles, Texas League (AA) - 1 game 20-Jul
- J.D. Orr (outfielder, b. 1996, Ohio)
- 2021: Jupiter Hammerheads, Low-A Southeast - 1 game 22-Jun
- 2021: Pensacola Blue Wahoos, Double-A South - 1 game 24-Jul
- 2022: Pensacola Blue Wahoos, Southern League (AA) - 1 game 14-Jul
- 2023: Pensacola Blue Wahoos, Southern League (AA) - 1 game 20-Apr
- Kyle Orr (first baseman, b. 1988, British Columbia)
- 2009: Ogden Raptors, Pioneer League (rookie) - 1 game 17-Aug
- Pete Orr (infielder, b. 1979, Ontario)
- 2005: Atlanta Braves, Major League Baseball - 1 game 6-Aug
- 2008: Washington Nationals, Major League Baseball - 2 games 22-Jun 10-Sep
- 2009: Washington Nationals, Major League Baseball - 1 game 20-Sep
- 2010: Syracuse Chiefs, International League (AAA) - 1 game 30-Jul
- 2011: Lehigh Valley IronPigs, International League (AAA) - 1 game 5-Aug
- 2012: Lehigh Valley IronPigs, International League (AAA) - 2 games 3-Jul 22-Jul
- 2014: Nashville Sounds, Pacific Coast League (AAA) - 1 game 21-Aug g2
- Sam Orr (infielder, b. 1983, California)
- 2005: Lakewood BlueClaws, South Atlantic League (Low-A) - 1 game 7-Apr
- Joe Orsulak (outfielder, b. 1962, New Jersey)
- Kaleb Ort (pitcher, b. 1992, Michigan)
- 2017: Staten Island Yankees, New York-Penn League (short-season) - 1 game 12-Sep
- 2018: Trenton Thunder, Eastern League (AA) - 1 game 20-Jun
- 2022: Boston Red Sox, Major League Baseball - 1 game 2-Oct
- 2024: Houston Astros, Major League Baseball - 1 game 12-Aug
- Jorge Orta (infielder, b. 1950, Mexico)
- 1976: Chicago White Sox, American League (MLB) - 1 game 9-Jul
- Bill Ortega (outfielder, b. 1975, Cuba)
- 2001: Memphis Redbirds, Pacific Coast League (AAA) - 1 game 3-Aug
- Bryce Ortega (infielder, b. 1988, California)
- 2012: Hagerstown Suns, South Atlantic League (Low-A) - 1 game 9-Aug
- Dennis Ortega (catcher, b. 1997, Venezuela)
- 2016: GCL Cardinals, Gulf Coast League (rookie) - 2 games 29-Aug g1 29-Aug g2
- 2019: Palm Beach Cardinals, Florida State League (High-A) - 1 game 11-May g1
- 2021: Memphis Redbirds, Triple-A East - 1 game 23-Sep
- Fernando Ortega (pitcher, b. 2001, Dominican Republic)
- 2023: FCL Phillies, Florida Complex League (rookie) - 1 game 10-Jun
- Hector Ortega (utility, b. 1972, Venezuela)
- 1992: Rockford Expos, Midwest League (Low-A) - 1 game 13-Aug
- Irving Ortega (infielder, b. 1996, Dominican Republic)
- 2017: Aberdeen IronBirds, New York-Penn League (short-season) - 1 game 16-Aug
- Jorel Ortega (infielder, b. 2001, Puerto Rico)
- Jose Ortega (pitcher, b. 1988, Venezuela)
- 2015: New Britain Rock Cats, Eastern League (AA) - 2 games 9-Aug 16-Aug
- 2018: Road Warriors, Atlantic League (independent) - 1 game 26-Jul g2
- 2019: Lincoln Saltdogs, American Association (independent) - 1 game 6-Jun
- Luis Ortega (pitcher, b. 1993, Dominican Republic)
- 2015: Wisconsin Timber Rattlers, Midwest League (Low-A) - 1 game 2-Sep
- Luis Ortega (infielder, b. 1993, Venezuela)
- 2016: Columbia Fireflies, South Atlantic League (Low-A) - 2 games 2-Jul 3-Sep
- Oliver Ortega (pitcher, b. 1996, Dominican Republic)
- 2018: Burlington Bees, Midwest League (Low-A) - 1 game 5-Aug
- Pablo Ortega (pitcher, b. 1976, Mexico)
- 1999: Orlando Rays, Southern League (AA) - 1 game 3-Jul
- Rafael Ortega (outfielder, b. 1991, Venezuela)
- 2018: Miami Marlins, Major League Baseball - 2 games 12-Sep 30-Sep
- 2019: Gwinnett Stripers, International League (AAA) - 1 game 1-May
- 2019: Atlanta Braves, Major League Baseball - 2 games 13-Aug 29-Sep
- 2023: New York Mets, Major League Baseball - 2 games 6-Sep 28-Sep
- 2024: Chicago White Sox, Major League Baseball - 2 games 7-May 8-May
- 2024: Charlotte Knights, International League (AAA) - 1 game 20-Sep
- Raul Ortega (infielder, b. 1984, Venezuela)
- Raul Ortega (catcher, b. 1999, New Jersey)
- 2024: Northern Colorado Owlz, Pioneer League (independent) - 1 game 5-Jul g1
- Wilbert Ortega (pitcher, b. 1977, Mexico)
- 1998: Clinton LumberKings, Midwest League (Low-A) - 1 game 20-Aug
- Wilmer Ortega (pitcher, b. 2001, Venezuela)
- 2023: Palm Beach Cardinals, Florida State League (Low-A) - 1 game 6-Jul
- Yunior Ortega (pitcher, b. 1991, Dominican Republic)
- 2012: Lowell Spinners, New York-Penn League (short-season) - 1 game 25-Aug
- Abimelec Ortiz (outfielder, b. 2002, Puerto Rico)
- 2023: Surprise Saguaros, Arizona Fall League - 1 game 13-Oct
- Asbel Ortiz (infielder, b. 1976, Puerto Rico)
- 2000: Newark Bears, Atlantic League (independent) - 1 game 6-Jul
- 2000: Aberdeen Arsenal, Atlantic League (independent) - 1 game 14-Sep
- 2001: Lehigh Valley Black Diamonds, Atlantic League (independent) - 3 games 15-Aug 30-Aug g1 30-Aug g2
- 2003: Road Warriors, Atlantic League (independent) - 3 games 12-Sep g1 12-Sep g2 14-Sep
- 2004: Bridgeport Bluefish, Atlantic League (independent) - 1 game 12-Sep
- Basilio Ortiz (outfielder, b. 1970, Connecticut)
- 1993: Frederick Keys, Carolina League (High-A) - 1 game 8-Aug
- Danny Ortiz (outfielder, b. 1990, Puerto Rico)
- 2015: Rochester Red Wings, International League (AAA) - 2 games 4-Jul 7-Sep
- 2017: Indianapolis Indians, International League (AAA) - 1 game 1-Sep
- 2018: Lehigh Valley IronPigs, International League (AAA) - 5 games 2-May 17-May 27-May 14-Jun 1-Aug g2
- 2022: Mayaguez Indios, Liga Clemente (winter) - 1 game 29-Nov
- Dario Ortiz (pitcher, b. 1982, Dominican Republic)
- 2003: Bristol Sox, Appalachian League (rookie) - 1 game 12-Jul
- David Ortiz (first baseman, b. 1975, Dominican Republic)
- 1997: New Britain Rock Cats, Eastern League (AA) - 1 game 3-Aug
- 2003: Boston Red Sox, Major League Baseball - 1 game 29-Jun
- 2016: Boston Red Sox, Major League Baseball - 2 games 25-Aug 28-Sep
- Hayder Ortiz (pitcher, b. 2001, Colombia)
- 2024: FCL Braves, Florida Complex League (rookie) - 1 game 22-Jun
- Hector Ortiz (catcher, b. 1969, Puerto Rico)
- 1996: Iowa Cubs, American Association (AAA) - 1 game 12-Aug
- 1998: Omaha Royals, Pacific Coast League (AAA) - 1 game 21-Aug g1
- Jankel Ortiz (infielder, b. 2004, Puerto Rico)
- 2023: FCL Twins, Florida Complex League (rookie) - 2 games 19-Jun 21-Aug
- Jhailyn Ortiz (outfielder, b. 1998, Dominican Republic)
- Joey Ortiz (infielder, b. 1998, California)
- 2022: Bowie Baysox, Eastern League (AA) - 1 game 24-Jun
- 2022: Norfolk Tides, International League (AAA) - 1 game 23-Sep
- 2023: Norfolk Tides, International League (AAA) - 1 game 15-Jul
- 2024: Milwaukee Brewers, Major League Baseball - 2 games 24-Sep 27-Sep
- Jonathan Ortiz (pitcher, b. 1985, Dominican Republic)
- 2007: Staten Island Yankees, New York-Penn League (short-season) - 1 game 22-Jul
- Jose Ortiz (infielder, b. 1977, Dominican Republic)
- 1998: Huntsville Stars, Southern League (AA) - 1 game 27-Aug
- Jose Ortiz (pitcher, b. 1977, Dominican Republic)
- 1999: Hudson Valley Renegades, New York-Penn League (short-season) - 1 game 10-Sep
- Jose Ortiz (catcher, b. 1994, Puerto Rico)
- 2014: Dayton Dragons, Midwest League (Low-A) - 1 game 30-Aug
- Julio Ortiz (pitcher, b. 2000, Dominican Republic)
- 2024: FCL Blue Jays, Florida Complex League (rookie) - 1 game 22-Jul
- 2024: Dunedin Blue Jays, Florida State League (Low-A) - 3 games 20-Aug 22-Aug 24-Aug
- Junior Ortiz (catcher, b. 1959, Puerto Rico)
- 1993: Cleveland Indians, American League (MLB) - 1 game 4-Sep
- Luis Ortiz (infielder, b. 1970, Dominican Republic)
- 1995: Texas Rangers, American League (MLB) - 1 game 16-Aug
- 1998: Omaha Royals, Pacific Coast League (AAA) - 1 game 21-Aug g1
- 2004: Edmonton Trappers, Pacific Coast League (AAA) - 1 game 15-Aug
- Luis Ortiz (pitcher, b. 1995, California)
- 2024: Clearwater Threshers, Florida State League (Low-A) - 2 games 23-Apr 25-Apr
- Luis Ortiz (pitcher, b. 1999, Dominican Republic)
- 2021: Bradenton Marauders, Low-A Southeast - 2 games 22-Jun 28-Jul
- Luis Ortiz (pitcher, b. 2000, Dominican Republic)
- Miguel Ortiz (infielder, b. 1979, Venezuela)
- 2000: Cedar Rapids Kernels, Midwest League (Low-A) - 1 game 13-Aug
- Mike Ortiz (first baseman, b. 1989, Florida)
- 2010: Hickory Crawdads, South Atlantic League (Low-A) - 1 game 11-Sep
- Nick Ortiz (infielder, b. 1973, Puerto Rico)
- 1996: Trenton Thunder, Eastern League (AA) - 2 games 20-Jul 27-Aug
- 1997: Trenton Thunder, Eastern League (AA) - 2 games 19-Aug 23-Aug night
- 1999: Akron Aeros, Eastern League (AA) - 1 game 1-Aug
- 2004: Bridgeport Bluefish, Atlantic League (independent) - 1 game 12-Sep
- 2006: Somerset Patriots, Atlantic League (independent) - 1 game 16-Aug
- 2007: Bridgeport Bluefish, Atlantic League (independent) - 1 game 14-Sep
- Ramon Ortiz (pitcher, b. 1973, Dominican Republic)
- 1999: Edmonton Trappers, Pacific Coast League (AAA) - 1 game 4-Jul
- 2011: Chicago Cubs, Major League Baseball - 1 game 11-Sep
- 2012: Scranton/Wilkes-Barre Yankees, International League (AAA) - 1 game 27-May
- Ray Ortiz (first base/outfield, b. 1968, California)
- 1994: Phoenix Firebirds, Pacific Coast League (AAA) - 1 game 31-Aug
- Ryan Ortiz (catcher, b. 1987, California)
- 2015: Laredo Lemurs, American Association (independent) - 1 game 31-Jul
- Steve Ortiz (pitcher, b. 1973, Texas)
- 1994: Burlington Indians, Appalachian League (rookie) - 1 game 3-Jul
- Wilberto Ortiz (infielder, b. 1985, Puerto Rico)
- 2012: Wichita Wingnuts, American Association (independent) - 1 game 28-Jul
- 2012: Lincoln Saltdogs, American Association (independent) - 1 game 24-Aug
- Yancarlos Ortiz (infielder, b. 1984, Dominican Republic)
- 2009: New Britain Rock Cats, Eastern League (AA) - 1 game 13-Sep
- Daniel Ortmeier (outfielder, b. 1981, Tennessee)
- 2002: Salem-Keizer Volcanoes, Northwest League (short-season) - 1 game 11-Aug
- Chad Orvella (pitcher, b. 1980, Washington)
- 2004: Bakersfield Blaze, California League (High-A) - 1 game 12-Aug
- Eric Orze (pitcher, b. 1997, Illinois)
- 2024: Syracuse Mets, International League (AAA) - 1 game 20-Sep
- Tanner Osberg (pitcher, b. 1982, Alberta)
- 2000: Kingsport Mets, Appalachian League (rookie) - 2 games 29-Jul 2-Aug
- 2002: Brooklyn Cyclones, New York-Penn League (short-season) - 1 game 30-Aug g2
- Drake Osborn (catcher, b. 1998, Texas)
- 2022: St. Lucie Mets, Florida State League (Low-A) - 1 game 17-Apr
- Patrick Osborn (infielder, b. 1981, California)
- 2008: Southern Maryland Blue Crabs, Atlantic League (independent) - 2 games 21-Jun 1-Sep
- 2009: Southern Maryland Blue Crabs, Atlantic League (independent) - 1 game 1-Oct
- 2010: Southern Maryland Blue Crabs, Atlantic League (independent) - 2 games 7-Sep g1 7-Sep g2
- Donovan Osborne (pitcher, b. 1969, California)
- 1993: St. Louis Cardinals, National League (MLB) - 1 game 25-Jun
- J.D. Osborne (catcher/first base, b. 1995, Ontario)
- 2018: Batavia Muckdogs, New York-Penn League (short-season) - 2 games 29-Jul 2-Aug
- 2021: Canada, Americas Olympic Qualifier - 1 game 31-May
- 2021: Pensacola Blue Wahoos, Double-A South - 1 game 24-Jul
- Mark Osborne (catcher/first base, b. 1978, North Carolina)
- 1998: South Bend Silver Hawks, Midwest League (Low-A) - 1 game 16-Aug
- Nick Osborne (outfielder, b. 1997, Tennessee)
- 2018: Vermont Lake Monsters, New York-Penn League (short-season) - 1 game 29-Jul
- Ryan Osborne (pitcher, b. 1996, New York)
- 2020: California Dogecoin, Liberation League (independent) - 1 game 23-Sep
- 2021: Wasco Reserve, Pecos League (independent) - 1 game 17-Jul
- Zach Osborne (pitcher, b. 1988, Texas)
- 2012: Myrtle Beach Pelicans, Carolina League (High-A) - 1 game 8-Aug
- Zach Osborne (infielder, b. 1990, Kentucky)
- 2014: Asheville Tourists, South Atlantic League (Low-A) - 1 game 5-Aug
- 2015: New Britain Rock Cats, Eastern League (AA) - 2 games 9-Aug 16-Aug
- 2016: Hartford Yard Goats, Eastern League (AA) - 1 game 5-Sep
- Jay O'Shaughnessy (pitcher, b. 1974, Massachusetts)
- 1998: Vero Beach Dodgers, Florida State League (High-A) - 1 game 8-Aug g2
- Ben O'Shea (pitcher, b. 1991, Massachusetts)
- 2012: Batavia Muckdogs, New York-Penn League (short-season) - 1 game 4-Aug
- Yuta Oshiro (infielder, b. 1993, Japan)
- 2016: Shikoku Island, Can-Am League (independent) - 1 game 16-Jun
- Keith Osik (catcher, b. 1968, New York)
- 1990: Welland Pirates, New York-Penn League (short-season) - 1 game 17-Aug
- 1999: Pittsburgh Pirates, National League (MLB) - 1 game 2-Oct
- Tyler Osik (pitcher, b. 1996, New York)
- 2022: Winston-Salem Dash, South Atlantic League (High-A) - 1 game 17-Jul
- Garret Osilka (infielder, b. 1977, Guam)
- 1998: Beloit Snappers, Midwest League (Low-A) - 2 games 15-Aug 19-Aug
- Mike Osinski (infielder, b. 1995, New York)
- 2021: Gastonia Honey Hunters, Atlantic League (independent) - 1 game 6-Aug
- Graham Osman (pitcher, b. 2001, Colorado)
- 2024: Daytona Tortugas, Florida State League (Low-A) - 1 game 17-May
- Mitchell Osnowitz (pitcher, b. 1991, Illinois)
- 2019: Springfield Cardinals, Texas League (AA) - 1 game 25-Jul
- 2021: Wichita Wind Surge, Double-A Central - 1 game 22-Jul
- Franquelis Osoria (pitcher, b. 1981, Dominican Republic)
- 2003: Vero Beach Dodgers, Florida State League (High-A) - 1 game 28-Aug
- Erik Ostberg (catcher/first base, b. 1995, Massachusetts)
- 2018: Hudson Valley Renegades, New York-Penn League (short-season) - 3 games 18-Jun 6-Sep 9-Sep
- 2021: Bowling Green Hot Rods, High-A East - 1 game 1-Jul
- Cooper Osteen (infielder, b. 1982, Florida)
- Gavin Osteen (pitcher, b. 1969, Delaware)
- 1997: Bowie Baysox, Eastern League (AA) - 1 game 17-Aug
- 1998: Rochester Red Wings, International League (AAA) - 1 game 1-Aug
- 2002: Camden Riversharks, Atlantic League (independent) - 1 game 11-Sep
- Matt Osterberg (pitcher, b. 1999, Wisconsin)
- Jimmy Osting (pitcher, b. 1977, Kentucky)
- 2001: Mobile BayBears, Southern League (AA) - 1 game 4-Aug
- Ian Ostlund (pitcher, b. 1978, Virginia)
- 2006: Erie SeaWolves, Eastern League (AA) - 1 game 3-Jul
- Rick Ostopowicz (outfielder, b. 1967)
- 1989: Pittsfield Mets, New York-Penn League (short-season) - 1 game 2-Sep
- Pat O'Sullivan (first base/outfielder, b. 1977, Illinois)
- 2005: Edinburg Roadrunners, Central League (independent) - 1 game 17-Aug
- Ryan O'Sullivan (pitcher, b. 1990, California)
- 2014: Scottsdale Scorpions, Arizona Fall League - 1 game 9-Oct
- 2015: Reading Fightin Phils, Eastern League (AA) - 1 game 17-Jun
- Al Osuna (pitcher, b. 1965, California)
- 1992: Houston Astros, National League (MLB) - 1 game 18-Aug
- 1993: Houston Astros, National League (MLB) - 1 game 15-Aug
- Alejandro Osuna (outfielder, b. 2002, Mexico)
- 2021: Down East Wood Ducks, Low-A East - 1 game 17-Jun
- 2024: Surprise Saguaros, Arizona Fall League - 2 games 11-Oct 12-Oct
- Alexis Osuna (catcher, b. 1976)
- Antonio Osuna (pitcher, b. 1973, Mexico)
- 1997: Los Angeles Dodgers, National League (MLB) - 1 game 29-Aug
- Jose Osuna (first base/outfield, b. 1992, Venezuela)
- 2015: Altoona Curve, Eastern League (AA) - 1 game 22-Aug
- 2018: Pittsburgh Pirates, Major League Baseball - 1 game 22-Sep
- Renny Osuna (infielder, b. 1985, Venezuela)
- 2008: Bakersfield Blaze, California League (High-A) - 1 game 2-Aug
- 2015: Southern Maryland Blue Crabs, Atlantic League (independent) - 1 game 24-May
- Roberto Osuna (pitcher, b. 1995, Mexico)
- 2015: Toronto Blue Jays, Major League Baseball - 1 game 12-Sep g1
- 2019: Houston Astros, Major League Baseball - 2 games 28-Mar 19-Jul
- Stiven Osuna (pitcher, b. 1987, Venezuela)
- 2009: Fort Wayne TinCaps, Midwest League (Low-A) - 1 game 29-Jul
- Corey Oswalt (pitcher, b. 1993, California)
- 2012: Kingsport Mets, Appalachian League (rookie) - 1 game 16-Aug
- 2018: New York Mets, Major League Baseball - 2 games 9-Jul g2 15-Jul
- Roy Oswalt (pitcher, b. 1977, Mississippi)
- 2000: Round Rock Express, Texas League (AA) - 1 game 24-Aug
- 2008: Houston Astros, Major League Baseball - 1 game 22-Aug
- Scott Ota (outfielder, b. 1997, California)
- 2023: St. Lucie Mets, Florida State League (Low-A) - 1 game 11-May
- Hideyoshi Otake (pitcher, b. 1988, Japan)
- 2015: Schaumburg Boomers, Frontier League (independent) - 1 game 30-Aug
- Hansel Otamendi (outfielder, b. 2002, Cuba)
- 2022: Palm Beach Cardinals, Florida State League (Low-A) - 1 game 15-Apr
- Johan Otanez (pitcher, b. 2002, Dominican Republic)
- 2023: Fredericksburg Nationals, Carolina League (Low-A) - 1 game 7-Sep
- Willis Otanez (infielder, b. 1973, Puerto Rico)
- 1997: Rochester Red Wings, International League (AAA) - 1 game 24-Aug
- 1998: Rochester Red Wings, International League (AAA) - 1 game 1-Aug
- 2003: Bowie Baysox, Eastern League (AA) - 1 game 5-Apr
- 2004: Bridgeport Bluefish, Atlantic League (independent) - 1 game 12-Sep
- 2005: Bridgeport Bluefish, Atlantic League (independent) - 2 games 25-Aug 11-Sep
- 2006: Bridgeport Bluefish, Atlantic League (independent) - 1 game 10-Sep
- 2008: Newark Bears, Atlantic League (independent) - 5 games 24-Aug 1-Sep 13-Sep g1 13-Sep g2 17-Sep
- 2009: Newark Bears, Atlantic League (independent) - 4 games 31-Aug 25-Sep 26-Sep 27-Sep
- 2011: Camden Riversharks, Atlantic League (independent) - 1 game 9-Sep
- Dan Otero (pitcher, b. 1985, Florida)
- 2018: Cleveland Indians, Major League Baseball - 1 game 20-Sep
- Elias Otero (infielder, b. 1987, Puerto Rico)
- 2009: Hudson Valley Renegades, New York-Penn League (short-season) - 2 games 5-Aug 2-Sep
- 2010: Hudson Valley Renegades, New York-Penn League (short-season) - 1 game 5-Sep
- Ricky Otero (outfielder, b. 1972, Puerto Rico)
- Sharif Othman (catcher, b. 1989, California)
- 2017: Trenton Thunder, Eastern League (AA) - 1 game 4-Jul
- 2018: Jacksonville Jumbo Shrimp, Southern League (AA) - 1 game 27-Aug
- Amos Otis (outfielder, b. 1947, Illinois)
- 1974: Kansas City Royals, American League (MLB) - 1 game 25-Apr
- John Otness (catcher/infielder, b. 1981, Washington)
- 2006: Wilmington Blue Rocks, Carolina League (High-A) - 1 game 14-Apr
- 2008: Portland Sea Dogs, Eastern League (AA) - 1 game 4-Aug
- Akinori Otsuka (pitcher, b. 1972, Japan)
- 2004: San Diego Padres, Major League Baseball - 1 game 8-Aug
- Thom Ott (pitcher, b. 1980, Florida)
- 2002: South Georgia Waves, South Atlantic League (Low-A) - 1 game 24-Aug
- Travis Ott (pitcher, b. 1995, Pennsylvania)
- 2014: Auburn Doubledays, New York-Penn League (short-season) - 1 game 4-Jul g1
- Paul Ottavinia (outfielder, b. 1973, New Jersey)
- 1998: Tampa Yankees, Florida State League (High-A) - 1 game 8-Aug g2
- 2001: Norwich Navigators, Eastern League (AA) - 1 game 15-Jul
- 2004: Somerset Patriots, Atlantic League (independent) - 3 games 22-May 19-Jun g1 19-Jun g2
- Adam Ottavino (pitcher, b. 1985, New York)
- 2006: State College Spikes, New York-Penn League (short-season) - 1 game 4-Jul
- 2018: Colorado Rockies, Major League Baseball - 1 game 6-May
- 2019: New York Yankees, Major League Baseball - 1 game 24-Sep
- 2021: Boston Red Sox, Major League Baseball - 1 game 1-Sep
- 2022: New York Mets, Major League Baseball - 1 game 3-May g1
- 2023: New York Mets, Major League Baseball - 1 game 7-Jun
- 2024: New York Mets, Major League Baseball - 2 games 4-May 27-Sep
- Micah Ottenbreit (pitcher, b. 2003, Michigan)
- Glenn Otto (pitcher, b. 1996, Texas)
- William Ouellette (pitcher, b. 1993, California)
- 2019: Dunedin Blue Jays, Florida State League (High-A) - 2 games 5-Apr 9-May
- Mark Outlaw (pitcher, b. 1977, Texas)
- 2002: Reading Phillies, Eastern League (AA) - 1 game 8-May
- 2003: Reading Phillies, Eastern League (AA) - 1 game 3-Apr
- James Outman (outfielder, b. 1997, California)
- 2019: Great Lakes Loons, Midwest League (Low-A) - 1 game 30-May
- 2021: Glendale Desert Dogs, Arizona Fall League - 1 game 20-Oct
- Josh Outman (pitcher, b. 1984, Missouri)
- 2013: Colorado Rockies, Major League Baseball - 1 game 28-Aug
- 2014: Columbus Clippers, International League (AAA) - 1 game 23-Aug
- 2014: New York Yankees, Major League Baseball - 1 game 19-Sep
- 2018: New Britain Bees, Atlantic League (independent) - 2 games 10-Jun 16-Jun
- Edward Ovalle (outfielder, b. 1985, Dominican Republic)
- 2009: Nashua Defenders, Can-Am League (independent) - 2 games 10-Aug 13-Aug
- Alexander Ovalles (first base/outfield, b. 2000, Dominican Republic)
- 2021: Charleston RiverDogs, Low-A East - 1 game 18-Jun
- 2022: Bowling Green Hot Rods, South Atlantic League (High-A) - 1 game 16-Aug
- Homy Ovalles (infielder, b. 1976, Venezuela)
- 2008: Alexandria Aces, United League (independent) - 1 game 13-Aug
- Layonel Ovalles (pitcher, b. 2003, Dominican Republic)
- 2022: St. Lucie Mets, Florida State League (Low-A) - 2 games 12-Aug 18-Sep
- 2023: St. Lucie Mets, Florida State League (Low-A) - 1 game 30-Apr
- Juan Carlos Ovalles (pitcher, b. 1982, Venezuela)
- 2007: Alexandria Aces, United League (independent) - 1 game 16-Aug
- 2008: Alexandria Aces, United League (independent) - 1 game 13-Aug
- Lyle Overbay (first baseman, b. 1977, Washington)
- 2000: El Paso Diablos, Texas League (AA) - 1 game 21-Aug
- 2005: Milwaukee Brewers, Major League Baseball - 1 game 3-Aug
- 2008: Toronto Blue Jays, Major League Baseball - 1 game 29-Aug
- 2009: Toronto Blue Jays, Major League Baseball - 1 game 4-Oct
- 2010: Toronto Blue Jays, Major League Baseball - 1 game 31-Jul
- 2013: New York Yankees, Major League Baseball - 2 games 12-Aug 25-Sep
- Cody Overbeck (infielder, b. 1986, Tennessee)
- 2011: Reading Phillies, Eastern League (AA) - 1 game 5-May
- 2011: Lehigh Valley IronPigs, International League (AAA) - 2 games 5-Aug 17-Aug
- 2012: Lehigh Valley IronPigs, International League (AAA) - 2 games 3-Jul 22-Jul
- 2013: Lehigh Valley IronPigs, International League (AAA) - 1 game 2-Sep
- Seth Overbey (pitcher, b. 1984, Utah)
- 2009: New Jersey Jackals, Can-Am League (independent) - 3 games 13-Aug 1-Sep 3-Sep
- 2010: New Jersey Jackals, Can-Am League (independent) - 1 game 31-May
- Pat Overholt (pitcher, b. 1984, Utah)
- 2006: Lakewood BlueClaws, South Atlantic League (Low-A) - 1 game 26-Apr
- 2007: Reading Phillies, Eastern League (AA) - 1 game 24-Aug g2
- 2008: Reading Phillies, Eastern League (AA) - 1 game 4-Aug
- 2009: Reading Phillies, Eastern League (AA) - 1 game 11-Apr
- 2010: Lancaster Barnstormers, Atlantic League (independent) - 1 game 18-Aug
- Kyle Overstreet (catcher, b. 1993, Alabama)
- 2017: Fort Wayne TinCaps, Midwest League (Low-A) - 1 game 19-Aug
- 2019: Amarillo Sod Poodles, Texas League (AA) - 1 game 25-Jul
- Connor Overton (pitcher, b. 1993, Virginia)
- 2022: Cincinnati Reds, Major League Baseball - 1 game 30-Sep
- Eduardo Oviedo (outfielder, b. 2004, Dominican Republic)
- 2024: FCL Pirates, Florida Complex League (rookie) - 1 game 4-May
- Johan Oviedo (pitcher, b. 1998, Cuba)
- 2022: St. Louis Cardinals, Major League Baseball - 1 game 8-Jun
- 2023: Pittsburgh Pirates, Major League Baseball - 1 game 27-Sep
- Ramon Oviedo (pitcher, b. 1990, Dominican Republic)
- 2013: Lakewood BlueClaws, South Atlantic League (Low-A) - 1 game 8-Aug
- Andy Owen (outfielder, b. 1973, Arizona)
- 1998: Elmira Pioneers, Northeast League (independent) - 1 game 7-Aug
- Dylan Owen (pitcher, b. 1986, South Carolina)
- 2007: Brooklyn Cyclones, New York-Penn League (short-season) - 2 games 5-Sep 10-Sep
- Harry Owen (catcher, b. 2002, California)
- 2022: FCL Braves, Florida Complex League (rookie) - 1 game 22-Aug
- Jack Owen (pitcher, b. 1998, Florida)
- 2023: Lansing Lugnuts, Midwest League (High-A) - 1 game 28-Jun
- Ryan Owen (catcher, b. 1980, Kansas)
- 2002: Great Falls Dodgers, Pioneer League (rookie) - 1 game 5-Aug
- 2004: Long Island Ducks, Atlantic League (independent) - 1 game 9-May
- Ryan Owen (pitcher, b. 1984, California)
- 2006: Hudson Valley Renegades, New York-Penn League (short-season) - 1 game 13-Aug
- Spike Owen (infielder, b. 1961, Texas)
- 1992: Montreal Expos, National League (MLB) - 2 games 5-Sep 20-Sep
- 1993: New York Yankees, American League (MLB) - 3 games 2-Sep 3-Sep 3-Oct
- Hagen Owenby (catcher/first base, b. 1995, Tennessee)
- 2017: Danville Braves, Appalachian League (rookie) - 1 game 28-Aug
- 2019: Rome Braves, South Atlantic League (Low-A) - 1 game 28-May
- Billy Owens (first baseman, b. 1971, California)
- 1992: Kane County Cougars, Midwest League (Low-A) - 1 game 11-Aug
- 1994: Bowie Baysox, Eastern League (AA) - 1 game 10-Jul
- Brad Owens (infielder, b. 1971)
- 1992: Hamilton Redbirds, New York-Penn League (short-season) - 1 game 9-Aug g2
- Eric Owens (outfielder, b. 1971, Virginia)
- 2001: Florida Marlins, Major League Baseball - 2 games 31-Jul 31-Aug
- 2002: Florida Marlins, Major League Baseball - 2 games 3-Sep g1 3-Sep g2
- Henry Owens (pitcher, b. 1979, Florida)
- 2002: Williamsport Crosscutters, New York-Penn League (short-season) - 1 game 7-Sep
- Henry Owens (pitcher, b. 1992, California)
- 2017: Portland Sea Dogs, Eastern League (AA) - 1 game 18-Aug g1
- Jeremy Owens (outfielder, b. 1976, Tennessee)
- 2003: Portland Sea Dogs, Eastern League (AA) - 2 games 4-Aug 12-Aug
- 2005: Somerset Patriots, Atlantic League (independent) - 6 games 12-Jun 24-Jul 18-Sep 27-Sep 29-Sep 1-Oct
- 2006: Montgomery Biscuits, Southern League (AA) - 1 game 2-Sep
- 2007: Durham Bulls, International League (AAA) - 1 game 2-Sep
- 2008: Southern Maryland Blue Crabs, Atlantic League (independent) - 3 games 21-Jun 1-Sep 14-Sep
- 2009: Southern Maryland Blue Crabs, Atlantic League (independent) - 1 game 1-Oct
- 2010: Southern Maryland Blue Crabs, Atlantic League (independent) - 1 game 7-Sep g1
- 2012: Southern Maryland Blue Crabs, Atlantic League (independent) - 1 game 29-Sep
- Jerry Owens (outfielder, b. 1981, California)
- 2009: Chicago White Sox, Major League Baseball - 1 game 23-Apr
- Justin Owens (outfielder, b. 1979, Kentucky)
- 2003: Charleston Alley Cats, South Atlantic League (Low-A) - 3 games 6-May 5-Jul 13-Jul
- Mike Owens (pitcher/first base, b. 1967)
- 1990: Batavia Clippers, New York-Penn League (short-season) - 1 game 16-Aug
- Rick Owens (infielder, b. 1984, Mississippi)
- 2007: Amarillo Dillas, United League (independent) - 1 game 13-Aug
- Walter Owens (outfielder, b. 1973)
- 1994: Burlington Indians, Appalachian League (rookie) - 1 game 3-Jul
- Luke Owens-Bragg (infielder, b. 1974, California)
- 1996: Hudson Valley Renegades, New York-Penn League (short-season) - 2 games 4-Jul 7-Jul
- 1997: Charleston RiverDogs, South Atlantic League (Low-A) - 1 game 14-Aug
- Chris Owings (utility, b. 1991, South Carolina)
- 2016: Arizona Diamondbacks, Major League Baseball - 1 game 10-Aug
- 2018: Reno Aces, Pacific Coast League (AAA) - 1 game 15-Aug
- 2019: Kansas City Royals, Major League Baseball - 1 game 24-Apr
- 2019: Boston Red Sox, Major League Baseball - 1 game 22-Sep
- Chris Owings (utility, b. 1991, South Carolina)
- 2022: Scranton/Wilkes-Barre RailRiders, International League (AAA) - 1 game 24-Sep
- 2023: Indianapolis Indians, International League (AAA) - 1 game 1-Jul
- Connor Owings (utility, b. 1994, South Carolina)
- 2021: Gateway Grizzlies, Frontier League (independent) - 1 game 7-Aug
- Micah Owings (pitcher, b. 1982, Georgia)
- 2008: Arizona Diamondbacks, Major League Baseball - 1 game 28-Jul
- Avery Owusu-Asiedu (outfielder, b. 2003, Saskatchewan)
- Matthew Oxendine (infielder, b. 1983, Florida)
- 2006: Missoula Osprey, Pioneer League (rookie) - 1 game 24-Aug
- Billy Oxford (pitcher, b. 1995, Arizona)
- 2018: Brooklyn Cyclones, New York-Penn League (short-season) - 1 game 18-Jun
- Chris Oxspring (pitcher, b. 1977, Australia)
- 2011: Somerset Patriots, Atlantic League (independent) - 1 game 12-Sep
- Jose Oyervidez (pitcher, b. 1982, Texas)
- 2002: Idaho Falls Padres, Pioneer League (rookie) - 1 game 14-Aug
- Rich Ozarowski (infielder, b. 1974, Florida)
- 1998: West Michigan Whitecaps, Midwest League (Low-A) - 1 game 16-Aug
- Travis Ozga (infielder, b. 1986, Florida)
- 2012: Binghamton Mets, Eastern League (AA) - 1 game 28-May
- Daniel Ozoria (infielder, b. 2000, Dominican Republic)
- Fernery Ozuna (infielder, b. 1995, Dominican Republic)
- 2017: Visalia Rawhide, California League (High-A) - 1 game 1-Aug
- Marcell Ozuna (outfielder, b. 1990, Dominican Republic)
- 2010: Jamestown Jammers, New York-Penn League (short-season) - 1 game 8-Sep
- 2011: Greensboro Grasshoppers, South Atlantic League (Low-A) - 1 game 25-May
- 2014: Miami Marlins, Major League Baseball - 3 games 26-May 15-Sep 17-Sep
- 2015: New Orleans Zephyrs, Pacific Coast League (AAA) - 1 game 27-Jul
- 2015: Miami Marlins, Major League Baseball - 2 games 14-Sep 16-Sep
- 2016: Miami Marlins, Major League Baseball - 2 games 4-Jul 28-Aug
- 2018: St. Louis Cardinals, Major League Baseball - 2 games 1-Apr 20-Aug
- 2019: St. Louis Cardinals, Major League Baseball - 1 game 18-Sep
- 2020: Atlanta Braves, Major League Baseball - 1 game 13-Oct
- 2021: Atlanta Braves, Major League Baseball - 2 games 30-Apr 1-May
- 2022: Atlanta Braves, Major League Baseball - 3 games 3-May g1 3-May g2 26-Sep
- 2023: Atlanta Braves, Major League Baseball - 1 game 7-Jun
- 2024: Atlanta Braves, Major League Baseball - 1 game 17-Jun
- Pablo Ozuna (infielder, b. 1974, Dominican Republic)
- 2002: Calgary Cannons, Pacific Coast League (AAA) - 2 games 7-Aug 9-Aug
- 2002: Florida Marlins, Major League Baseball - 2 games 3-Sep g1 3-Sep g2
- 2006: Chicago White Sox, Major League Baseball - 1 game 30-Jul
- 2008: Los Angeles Dodgers, Major League Baseball - 1 game 27-Jul
- 2009: Lehigh Valley IronPigs, International League (AAA) - 1 game 12-Apr
- 2010: Newark Bears, Atlantic League (independent) - 1 game 6-Aug
- Rafael Ozuna (infielder, b. 1974, Dominican Republic)
- 2008: Alexandria Aces, United League (independent) - 1 game 13-Aug
- Reniel Ozuna (outfielder, b. 1998, Dominican Republic)
- 2019: Billings Mustangs, Pioneer League (rookie) - 1 game 4-Jul
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