In the summer of 2011 , Lesnar announced that he was returning to action , stating , " I feel like a new man . Healthy . Strong . I feel like I used to feel " . His return match was scheduled to be at UFC 141 on December 30 in Las Vegas against former Strikeforce heavyweight champion Alistair Overeem . Overeem won the fight by way of technical knockout in the first round . The result of the fight remains controversial , as Overeem tested positive for elevated levels of testosterone prior to his next fight . Lesnar then announced his retirement from MMA , mentioning his struggles with diverticulitis and saying " tonight was the last time you 'll see me in the octagon " .