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| Name | Pos | Team | Age | DOB | POB | Nationality | Bats | Throws | Height | Weight | Salary |
| O'Connor, Peter | RF | Lansing Lugnuts | 32 | 06/19/1986 | Waimea in Kauai County | USA | Right | Left | 6' 2" | 196 lbs | - |
| O'Connor, Rich | CL | Redwood City Redwoods | 33 | 07/02/1985 | Edinburg | USA | Right | Right | 6' 0" | 204 lbs | - |
| O'Donnell, Geoffrey | RF | San Jose Missions | 33 | 04/29/1985 | New York | USA | Right | Right | 6' 2" | 208 lbs | - |
| O'Rorke, Wendell | SP | Vancouver Vipers | 32 | 08/13/1986 | Trenton | USA | Switch | Right | 5' 10" | 185 lbs | - |
| O'Rourke, John | MR | District 9 Prawns | 32 | 05/13/1986 | Windemere | USA | Switch | Right | 6' 0" | 190 lbs | - |
| Ono, Kozue | 3B | Mexico City Cerveceros | 24 | 10/05/1994 | Osaka | JPN | Right | Right | 6' 2" | 205 lbs | - |
| Ontiveros, Juan | RF | Mexico City Cerveceros | 24 | 10/22/1994 | Little Rock | USA | Left | Left | 5' 11" | 185 lbs | - |
| Orozco, Guillermo | SP | Vancouver Vipers | 23 | 11/03/1995 | Barinas | VEN | Right | Left | 5' 9" | 230 lbs | - |
| Orozco, José | MR | Free Agent | 30 | 06/21/1988 | Monte Plata | DOM | Switch | Right | 6' 2" | 206 lbs | - |
| Ortíz, José | MR | Spokane Trappers | 24 | 03/06/1994 | Santo Domingo | DOM | Right | Right | 6' 0" | 208 lbs | - |
| Oshima, Masamune | MR | Free Agent | 29 | 08/12/1989 | Takeo | JPN | Right | Right | 6' 3" | 228 lbs | - |
| Otto, Sloan | SP | Houston Hammertime | 24 | 03/08/1994 | North Battleford | CAN | Right | Right | 5' 10" | 215 lbs | - |
| Ouellette, William | MR | Las Vegas Stars | 30 | 10/24/1988 | Cochrane | CAN | Right | Right | 6' 2" | 223 lbs | - |
