kim defeated the ultimate fighter season 5 winner, nate diaz on january 1, 2011, at ufc 125 via unanimous decision. kim used his judo to control rounds 1 and 2. diaz mounted a remarkable offense in round 3, but it was not enough and kim won a decision over diaz. after the fight kim called out current ufc welterweight champion, georges st-pierre, whom he considers a hero and role model to himself as a mixed martial artist. later on january 10, 2011, kim signed a four fight extension with the ufc.