"It will be an honor to fight St. Pierre," Condit said. "Georges is a guy I've looked up to since I was a kid, before the UFC."
Diaz pressed forward in the second round and appeared to get the better of the punches. But Condit landed leg kicks throughout the fight, and eventually was able to land effective counter strikes, giving him the win on all three scorecards, 48-47, 49-46, and 49-46.
"Nick's pace is second to none," Condit said. "Chopping down his legs and slowing his pace was definitely a part of the game plan."
Condit evaded the pressing attack from Diaz, constantly circling to his left and countering with kicks and punches and landed a solid roundhouse to Diaz's face in the fourth round.
"In other fights, I've come on strong in the later rounds and that's what I felt would happen tonight." Condit said. "My endurance has always been a strong point of mine. ... I think that has helped me in my fights."
Diaz was visibly upset when the decision was announced and hinted at retirement.
"I'm not going to accept this as a loss," Diaz said. "I think I'm done with this MMA stuff, I don't think they can pay me enough to do this again."
Diaz was originally scheduled to fight St. Pierre but was pulled from the bout due to disciplinary reasons, replaced by Condit, and relegated to the undercard of that fight in which he easily defeated B.J. Penn.
The fight between Condit and St. Pierre never happened as St. Pierre was forced to pull out due to injury which led to the matchup between Diaz and Condit for the interim title.
In the other co-main event, Fabricio Werdum earned a unanimous decision victory over Roy Nelson in his return to the UFC. Werdum, regarded as one of the best heavyweight jiu-jitsu practitioners in the world, dominated Nelson in a fight that was largely a stand-up battle.
Werdum landed powerful knees from the muay thai clinch in the first round, cutting Nelson across the bridge of the nose which bled throughout all three rounds and controlled the fight with a balanced mix of knees, kicks and punches.
I'm known for my ground game but I train for everything," Werdum said. "Roy has a great right hand but later in the fight, I could tell he was getting tired in the clinch and I felt strong from then on."
In other main card bouts, Josh Koscheck got a split-decision victory over Mike Pierce, Renan Barao earned a unanimous decision win over Scott Jorgensen and Ed Herman secured a rear-naked choke forcing Clifford Stark to tap in the second round.