Jack O'Brien (Denver Jack O'Brian) boxer
- bouts
- 7
- won
- 1
- lost
- 3
- draw
- 3
- Status
- inactive
- Division
- middleweight
- Debut
- 1919-11-26
- Height
- -
- Reach
- -
- Age
- -
- Born
- -
- Death
- -
- Nationality
- USA
| Date | Opponent | Last Opponents' Results | Place | Result |
|---|---|---|---|---|
| 1921-09-30 | Joe Black | DLWWLD | Stockyards Stadium, Denver | WIN |
| 1921-09-09 | Harry Reide | LDDDDW | Stockyards Stadium, Denver | DRAW Points |
| 1921-06-21 | Harry Reide | WLDDLD | Stockyards Stadium, Denver | DRAW Points |
| 1921-06-03 | George Eagel | DLWWDD | Jazzland Theatre, Casper | LOST Technical knockout |
| 1921-05-20 | Billy Williams | debut | Jazzland Theatre, Casper | DRAW Points |
| 1920-01-01 | Walter Caldwell | WW | Crystal Theater, Albuquerque | LOST Technical knockout |
| 1919-11-26 | Mack Dalton | D | Salt Lake City | LOST Technical knockout |