Jake O'Brien has four losses against four opponents on his MMA record. For a list of O'Brien's best fights, refer to "Best fights of Jake O'Brien".
On July 10, 2010 Jake O'Brien faced off against Gegard Mousasi in a light-heavyweight bout at age 25. He was coming in with a record of 13-4 (8), and Mousasi was 24 years old and with a record of 28-3-1 (26). O'Brien lost the fight via 1st-round submission.
On July 11, 2009 Jake O'Brien faced off against Jon Jones in a light-heavyweight bout at age 24. He was coming in with a record of 11-3 (7), and Jones was 21 years old and with a record of 8-0 (6). O'Brien lost the fight via 2nd-round submission.
On July 19, 2008 Jake O'Brien faced off against Cain Velasquez at age 23. He was coming in with a record of 10-2 (7), and Velasquez was 25 years old and with a record of 3-0 (3). O'Brien lost the fight via 1st-round TKO.
On March 1, 2008 Jake O'Brien faced off against Andrei Arlovski at age 23. He was coming in with a record of 10-1 (7), and Arlovski was 29 years old and with a record of 12-5 (11). O'Brien lost the fight via 2nd-round TKO.
