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| Player Index: 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 | |
| "O" Player Index | |
| Starts with "O" Career Batting Register
and Career Pitching Register Bold indicates a Hall of Famer. |
| Obando, Boris | 2018-2021 |
| Obando, Roque | 2011-2013 |
| Obermueller, Wes | 2004-2013 |
| O'Brien, Patrick | 2009-2016 |
| Ocasio, Mauro | 2020-2021 |
| Officer, Matthew | 2016-2021 |
| O'Keefe, Mike | 2006-2017 |
| Oliveira, Jose | 2016-2021 |
| Oliveira, Jose | 2015-2020 |
| Olivo, Miguel | 2003-2013 |
| Ollis, Leonard | 2017-2021 |
| Olmedo, Ranier | 2007-2015 |
| Olsen, Kevin | 2002-2007 |
| Olsen, Scott | 2014-2016 |
| Oquendo, Ian | 2007-2020 |
| Orcutt, John | 2011-2021 |
| Ordonez, Magglio | 1998-2011 |
| Orie, Kevin | 1998-2007 |
| O'Riordan, Chris | 2007-2013 |
| Orlowski, Derrick | 2021-2021 |
| Oropesa, Eddie | 2002-2009 |
| Ortega, Alejo | 2017-2021 |
| Ortego, Cristobal | 2009-2017 |
| Ortiz, Albert | 2011-2011 |
| Ortiz, Cesar | 2011-2020 |
| Ortiz, David | 1998-2008 |
| Ortiz, Javier | 2006-2013 |
| Ortiz, Jose | 2001-2007 |
| Ortiz, Russ | 1999-2008 |
| Ortiz, Tony | 2021-2021 |
| Ortiz, Valentin | 2020-2021 |
| Ortmeier, Dan | 2011-2017 |
| Osborn, Pat | 2011-2014 |
| Osoria, Franquelis | 2007-2016 |
| Osuna, Antonio | 1996-2009 |
| Oswalt, Roy | 2002-2015 |
| Ouimet, Larry | 2020-2021 |
| Ouimet, Marty | 2017-2021 |
| Overbay, Lyle | 2002-2012 |
| Owens, Eric | 1996-2009 |
| Ozuna, John | 2018-2020 |
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