| 12/31/2018 | ||||||
 |
|
| O |
| Name | Pos | Team | Age | DOB | POB | Nationality | Bats | Throws | Height | Weight | Salary |
| O'Day, Adrian | RF | Los Angeles Bruins | 31 | 10/21/1987 | Runnemede | USA | Left | Left | 6' 3" | 193 lbs | $2,000,000 |
| O'Kerwan, Jim | C | Free Agent | 30 | 02/20/1988 | Bethlehem | USA | Left | Right | 5' 11" | 208 lbs | - |
| O'Reilly, Cody | SP | Jacksonville Jackhammers | 25 | 02/14/1993 | San Leandro | USA | Right | Right | 6' 0" | 215 lbs | $400,000 |
| O'Rorke, Jonathan | 3B | Free Agent | 35 | 03/25/1983 | Colville | USA | Right | Right | 6' 0" | 192 lbs | - |
| O'Sullivan, Joe | SP | St Charles Sheens | 24 | 09/29/1994 | Augusta-Richmond County | USA | Right | Right | 6' 5" | 230 lbs | $800,000 |
| O'Tormey, Brian | MR | Kansas City Cougars | 30 | 09/26/1988 | Mansfield | USA | Right | Right | 5' 10" | 201 lbs | $1,200,000 |
| Ogusuku, Takafumi | MR | Indianapolis Lions | 23 | 08/18/1995 | Hojo | JPN | Right | Right | 6' 2" | 245 lbs | $650,000 |
| Oike, Okura | SP | Indianapolis Lions | 24 | 11/20/1994 | Shiroyama | JPN | Right | Right | 6' 3" | 230 lbs | $400,000 |
| Ojeda, António | MR | St. Louis Browns | 22 | 02/17/1996 | San Andrés | PAN | Right | Right | 6' 1" | 220 lbs | $400,000 |
| Ojeda, Orlando | MR | Los Angeles Bruins | 22 | 04/11/1996 | Fajardo | PUR | Right | Right | 6' 4" | 255 lbs | $1,200,000 |
| Oliva, Jorge | MR | Reno Cards | 23 | 11/03/1995 | Yamasa | DOM | Left | Right | 6' 1" | 200 lbs | - |
| Oliver, Ian | 1B | Jacksonville Jackhammers | 30 | 03/30/1988 | Enterprise | USA | Switch | Right | 6' 1" | 175 lbs | $400,000 |
| Ono, Takehide | MR | Maui Tropics | 23 | 02/04/1995 | Saitama | JPN | Right | Right | 6' 0" | 200 lbs | $3,500,000 |
| Onodera, Yasuhiko | 1B | St. Louis Browns | 22 | 11/06/1996 | Yokohama | JPN | Left | Right | 6' 0" | 200 lbs | $400,000 |
| Ontiveros, Ricardo | CL | Irvine Gang Green | 22 | 07/22/1996 | Río Grande | PUR | Right | Right | 6' 7" | 210 lbs | $650,000 |
| Ordóńez, Roberto | LF | Jacksonville Jackhammers | 24 | 01/22/1994 | Santo Domingo | DOM | Right | Right | 5' 9" | 200 lbs | $400,000 |
| Ortega, Alberto | SP | Orlando Calrissian | 24 | 08/17/1994 | Nezahualczyotl | MEX | Right | Right | 6' 1" | 215 lbs | $4,000,000 |
| Ortega, Júlio | 1B | Free Agent | 32 | 09/06/1986 | Copiapó | CHI | Left | Left | 6' 0" | 196 lbs | - |
| Ortega, Pedro | MR | San Francisco Bandits | 28 | 08/23/1990 | Managua | NCA | Right | Right | 5' 11" | 232 lbs | $1,100,000 |
| Ortíz, Anastasio | 1B | St Charles Sheens | 23 | 03/31/1995 | San Juan | PUR | Switch | Right | 6' 3" | 190 lbs | - |
| Ortíz, Guillermo | C | Vista Panthers | 28 | 08/28/1990 | Torrance | USA | Switch | Right | 6' 0" | 211 lbs | $400,000 |
| Ortíz, José | SS | Niagara Falls Frenzy | 31 | 01/15/1987 | Santiago de María | SLV | Right | Right | 6' 1" | 176 lbs | $650,000 |
| Ortíz, José | MR | Orlando Calrissian | 22 | 07/10/1996 | Tocumen | PAN | Right | Right | 6' 3" | 240 lbs | $400,000 |
| Ortíz, José | RF | Jersey Shore D-Bags | 30 | 08/11/1988 | Harrison | USA | Left | Left | 6' 1" | 195 lbs | $1,150,000 |
| Otero, Anastasio | MR | Free Agent | 30 | 12/22/1988 | Clinton | USA | Right | Right | 6' 0" | 200 lbs | - |
| Ou-yang, Qian-gui | 1B | Indianapolis Lions | 26 | 08/22/1992 | Juifang | TPE | Left | Right | 6' 1" | 198 lbs | $400,000 |
| Overbeek, Jordi | 2B | Toronto Titans | 31 | 09/12/1987 | Abcoude | NED | Right | Right | 5' 9" | 181 lbs | $7,260,000 |
| Owens, Kelly | RF | Cleveland Monsters | 27 | 04/04/1991 | Unionville | USA | Right | Right | 6' 0" | 210 lbs | $400,000 |
| Oyama, Takuya | 2B | Kansas City Cougars | 28 | 11/28/1990 | Tatebayashi | JPN | Right | Right | 5' 11" | 195 lbs | $2,800,000 |
