Penn, the 30-year-old UFC lightweight champion, fought off takedowns in the first rounds. St. Pierre, the 27-year-old UFC welterweight champion, grabbed a few single-legs but couldn't finish them, though he used his length on the feet to score points.
St. Pierre finally finished a single-leg to start the second. He was able to posture up and land a solid left hand to his Hawaiian opponent's jaw, which helped open a pass to side control. St. Pierre landed a right as well before Penn got his guard back. Penn showed his usual flexibility from the bottom, but he could not control St. Pierre, who punched and elbowed from the top, passed again and cut Penn below the eye.
It was a round that clearly belonged to St. Pierre and set the tone for the rest of the fight.
The French Canadian fighter fed Penn some jabs to open the third. Penn's nose began to leak blood, and St. Pierre began to dominate. On the ground, St. Pierre passed to side control and punished Penn with short punches and elbows.
By the fourth, Penn looked to be in bad shape. St. Pierre jabbed his face, buried a kick into his leg and put him on his back again. The round was all St. Pierre, who tied up Penn on the mat and continued to batter him with strikes.
Between rounds, Penn's corner called the fight.
"Last time I fought him, I won a decision," St. Pierre said. "This time I really wanted to take him out and I'm glad that I did. He's very tough."
Machida too much for Silva
The first time Machida dropped Silva was after a knee to the body and a left to the face. Later, Machida floored his foe again with a right hand that finished a combination. Then, with the round closing, Machida tripped Silva to the mat and planted a punch on his chin.
The horn sounded, but Silva didn't get up. Referee Yves Lavigne called the bout, the victory moving Machida's record to 14-0.
"Thiago was a tough guy, but today I was better than him," Machida said.
Jones passes Bonnar test
Despite having fought just once in the UFC, Jones' talent was superior to his opponent's experience in the light heavyweight bout. He threw Bonnar to his back early in the first. After Bonnar stood, Jones tossed him again and later suplexed him.
The 31-year-old Bonnar had a tough time striking, as well. Jones was unorthodox, throwing several spinning strikes like the elbow that dropped Bonnar on his cheek in the first round.
Jones seemed to tire in the second and third, which allowed Bonnar to rally with his hands. Before "The American Psycho" could do much damage, though, Jones would throw him back to the mat, ensuring the decision in his favor.
Parisyan rallies to conquer Kim
Kim, 27, was a step ahead throughout the first period. He tripped Parisyan to the mat, took his back and threatened briefly with an armbar and a triangle choke. The attempts missed, but Kim clearly controlled the round.
Parisyan, 26, of North Hollywood, Calif., won the second. He threw Kim and worked on a kimura. Kim got back to his feet, but Parisyan sent him flying through the air with a throw.
The fighters traded takedowns in the third but spent most of the round struggling in the clinch. It was a tough round to score and not one that pleased the fans, who booed the fight's conclusion and the decision.
Diaz stumbles against Guida
Guida's tenacity proved the deciding factor. Diaz, 23, of Stockton, Calif., had kept him on the end of his punches early in the first round. Despite his advantage on the feet, though, Diaz tried a takedown that failed and he ended up on his back. Guida, 27, began to push the pace, landing some elbows on the ground and later slamming Diaz.
In the second, Guida glued himself to his opponent's back. Diaz threw him to the canvas, but even then Guida would not let go.
The third was Diaz's best round. He peppered Guida's face and worked his body with punches, but the offense wasn't enough to avoid suffering his first defeat in the Octagon.
"I know it wasn't pretty, but it's a win, and like I said, I'm here and I'm coming for the top of the lightweight division," said Guida, a winner of three straight. "Be ready for me."
Fitch fights his way past Gono
Jon Fitch (18-3, 1 NC) dominated Pride Fighting Championships veteran Akihiro Gono en route to a convincing unanimous decision. Scores from the one-sided affair were 30-27, 30-27 and 30-26.
Based at the revered American Kickboxing Academy, Fitch nearly ended Gono's night with submissions in Rounds 1 and 2, first with a rear-naked choke and then with an armbar. That was a minor feat in itself, as the crafty Gono (29-14-7) has not raised the white flag in a fight in more than 12 years.
When Fitch was not stifling and tying Gono in knots on the mat, he fed him a steady diet of punches, elbows and forearms. The 30-year-old Fort Wayne, Ind., native was particularly impressive in the third round, when he punished Gono standing and on the ground from the knee-on-belly position. He left little doubt about the decision.
Tavares tames Gamburyan
Brazilian lightweight prospect Thiago Tavares picked up a much-needed unanimous decision victory against "The Ultimate Fighter 5" runner-up Manny Gamburyan. Scores were 29-28 from all three judges.
The outcome remained in question into the third round, when Tavares (14-3) rocked his Armenian counterpart with a right hand and vicious knee. Sensing he was hurtling toward a second consecutive defeat, Gamburyan grew desperate as precious seconds ticked away, swinging and missing wildly at his elusive target. His efforts proved fruitless.
The 27-year-old Gamburyan has not cracked the win column in almost a year. The judo black belt pressured Tavares with kimuras in the first and second round but slowly lost his foothold in the match. The victory snapped a two-fight losing streak for Tavares.
Joe Hall covers MMA for Sherdog.com.