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- Andy O'Brien, Vancouver Whitecaps FC
- Sammy Ochoa, Seattle Sounders FC
- Darren O'Dea, Toronto FC
- Dominic Oduro, Chicago Fire
- Amobi Okugo, Philadelphia Union
- Jámison Olave, Real Salt Lake
- Lawrence Olum, Sporting Kansas City
- Shane O'Neill, Colorado Rapids
- Ike Opara, San Jose Earthquakes
- Danny O'Rourke, Columbus Crew
- Karl Ouimette, Montreal Impact
- Brian Ownby, Houston Dynamo
Read more about this topic: List Of Current Major League Soccer Players