MONTREAL - UFC welterweight champion Georges St-Pierre manhandled Nick Diaz for five rounds en route to a lopsided unanimous decision at UFC 158 on Saturday night.
St-Pierre (24-2) pitched a shutout, winning 50-45 on all three judges' cards.
"Nick Diaz is a good guy," said the champion, looking to end the bad blood between the two.
Diaz, who said he was flat after a 13-month layoff, thanked St-Pierre "for giving him the credit I think I deserve."
Diaz came to the fight with a chip on his shoulder and plenty of attitude. He leaves with a loss and lumps on his face, although he showed the champion respect after the fight.
As expected, St-Pierre used his wrestling to control the chirpy challenger, rag-dolling him at times and bullying him on the ground. But he also used his jab and kicks to pick apart the challenger on his feet.
A calm, calculating St-Pierre won almost every battle during the fight without putting himself in harm's way. Diaz (27-8-0 with one no contest) never quit, but showed less of his trademark trash-talking. He had his hands full.
The main event had been rife with animosity, with Diaz showing St-Pierre little respect. The normally calm champion was red-hot coming into the fight, saying he wanted to "retire" Diaz.
He may have done it. Diaz said his fighting days may be over.
"I think I'm done with this mixed martial arts," he said.
In the lead up to the fight, Diaz skipped a public workout, then put on a strange one-man show at the pre-fight news conference that managed to befuddle and antagonize St-Pierre.
"I never took it personally," the champion said after the fight.
The antagonism continued right up to the fight with fellow fighter Jake Shields, a member of the Diaz entourage, complaining about St-Pierre's hand wraps.
"I checked GSP's glove and the wrap looked shady," Shields, beaten by GSP at UFC 129, tweeted before the fight.
UFC President Dana White said Shields had OK'd the wrap, only to have another member of Diaz's camp complain later.
The 31-year-old from Montreal was looking for his eighth straight successful title defense since winning his 170-pound championship back from Matt Serra at UFC 83 in April 2008. Only middleweight champion Anderson Silva has more title defenses (10).
The welterweight contenders' picture grew clearer earlier in the main card as Jonny Hendricks (15-1) won a unanimous 29-28 decision over Carlos Condit (28-7) in a wild co-main event that left both men blooded, and with the respect of their boss.
"These boys are holding nothing back," tweeted an appreciative White.
Hendricks, who said he broke his left hand in the fight, was promised a title shot if he won.
"Guess what, I earned it," said Hendricks.
Diaz came out to a chorus of boos, one man against a champion backed by thousands in the stands. He calmly walked inside the cage, his four corner men urging him on.
Then the lights dimmed and St-Pierre followed, bouncing up and down in his traditional karate garb to pulsating French-language rap. The crowd erupted.
Diaz walked over to the cage and yelled something as St-Pierre prepared to enter. It didn't seem like a hello. Montreal referee Yves Lavigne then moved over to keep a close watch on the challenger.
The place was rocking before the cage doors closed.
St-Pierre's first takedown came seconds later. Diaz looked to work a submission, but the champion controlled him, firing punches as Diaz tried to get up. A pair of elbows produced a knot on the challenger's forehead.
The crowd started chanting "Ole! Ole!" St-Pierre responded by dropping Diaz on his head, capping a dominant first round.
St-Pierre landed another takedown 40 seconds into the second round and soon had Diaz on his knees face down again, hitting him with knees and punches. Diaz's face was showing damage.
Diaz tried to get in the champ's face as the round ended.
Diaz went down again in the third, after eating some punches. When Diaz got back up, he fired some leg kicks and scored with some jabs. Then St-Pierre dumped him, battering him on the ground.
Diaz flicked a punch after the bell at St-Pierre, whose face was bloodied.
Both men looked tired in the fourth, but St-Pierre scored another takedown and Diaz soon had the champion clamped to him again.
The two clinched in the fifth before Diaz fell attempting a kick. St-Pierre jumped on him and Diaz was again face down on the mat. The fight finished fittingly with St-Pierre on top and the crowd roaring.
The two shook hands, hugged and Diaz raised St-Pierre's hand.
The champion came into Saturday's fight on a 10-bout win streak. And needing just three rounds to erase Randy Couture's UFC record of 44 championship rounds fought.
It was St-Pierre's 13th championship fight, second only to the retired Couture (15).
Condit was initially due to face Rory MacDonald but the Montreal fighter had to pull out with a neck injury. That forced a reshuffle of the welterweight bouts with Hendricks moved to face Condit and Marquardt brought in to take on Ellenberger.
Ellenberger (29-6) made short work of Marquardt (35-12-2), knocking him down with a left-right and then hurting him with another. Marquardt did not seem to like the stoppage by Philippe Chartier, at 3:00, but he was dazed and vulnerable.