The 27-year-old St. Pierre, who won a split decision when the two met at UFC 58 in March 2006, was leading heavily on all three scorecards when referee Herb Dean stopped the bout on the advice of ringside doctors. Penn’s corner agreed with the decision.
“Last time I fought him I won in a decision,” St. Pierre said. “This time I really wanted to take him out, and I’m glad I did.”
In the co-feature, Lyoto Machida knocked out Thiago Silva with a second left in the first round to win a matchup of undefeated light heavyweights.
There was no doubt what drew a cheering crowd to the MGM Grand Garden, though.
St. Pierre was all over Penn from the outset, pressing him against the fence for most of the first round and taking him down almost at will throughout the next three rounds.
The Canadian fighter wound up on top of Penn in the fourth round and kept dropping elbows and landing punches. Dean nearly stopped the fight as Penn kept absorbing the damage, but the Hawaiian fighter managed to make it to the end of the round.
When asked who he wants to fight next, St. Pierre replied: “I’m a world champion and a proud champion. So I want to fight the best.”
Earlier in the night, Machida floored Silva multiple times in the first round before landing a devastating shot that ended the match.
The victory places Machida near the top of the talent-laden light heavyweight division. Asked who he wanted to fight next, Machida turned to the crowd and said, “People, do I deserve a title shot?” The crowd responded with cheering approval.
In the undercard fights, Jon Jones won by unanimous decision over Stephan Bonner; Karo Parisyan earned a split decision victory over Dong Hyun Kim; and Clay Guida defeated Nate Diaz by split decision.
In the preliminary bouts, Jon Fitch won by unanimous decision over Akihiro Gono; Thiago Tavares defeated Manvel Gamburyan by unanimous decision; and John Howard beat Chris Wilson by split decision. Jake O’Brien defeated Christian Wellisch by split decision and Dan Cramer won by split decision over Matt Arroyo.
