Part of challenger Diego Sanchez's strategy seemed to be to take out UFC lightweight champ BJ Penn's leg.

That played right into Penn's game plan.

"It's a blessing when a guy grabs my leg," Penn said, "because I know that's my chance to hit him. They're usually running away, and I've got to wait to hit them. If he grabs the leg, I can just keep hitting him."

Penn, used the counter-punching to retain his UFC lightweight championship Saturday night with a fifth-round TKO of Sanchez in the main event of UFC 107.

Referee Herb Dean, with the advice of the ringside doctor, stopped the fight at 2:37 of the round after Penn's kick caught Sanchez, opening a gaping gash above the challenger's left eye.

UFC president Dana White said Sanchez was taken to a hospital.

"He was about as busted up as I've ever seen a guy," White said.

Penn, undefeated at 155 pounds for the past eight years, methodically attacked Sanchez through the first four rounds, mainly with punches and defending against Sanchez's attempts to take out the champion's legs.

Penn said the challenger took some big shots and recovered quickly in the first round, but it seemed to take a lot out of Sanchez.

"Instead of going forward, I think he got kind of bummed out on that," Penn said of Sanchez's initial offense. "He was kind of backing up and moving around the ring.

"After the first round, he started backing up a little bit, but he never totally gave up the fight."

The crowd was clearly in Penn's corner, unleashing chants of "BJ! BJ!" throughout the bout.

In the semifinal, former heavyweight champion Frank Mir made quick work of Cheick Kongo, winning by submission with 1:12 gone in the opening round. It was Mir's first fight since losing the championship to Brock Lesnar in July.

Mir and Kongo had a battle of words in the days leading up to the fight. Kongo had said Mir was a big mouth and he was going to stop the former champ's talk.

Kongo didn't get much of a chance. The two circled each other at first, but about 40 seconds in, Mir rocked Kongo with a left hand to the chin, sending him to the mat.

Mir immediately followed with more punches, and then locked in a guillotine choke. Kongo was unconscious when Dean lifted his arm to check, the hand dropping to Kongo's leg.

When Mir released the hold and began his celebration, Kongo tumbled over on his back limply, sending his corner into the ring. He eventually walked out as Mir called for another chance to get the heavyweight championship back.

"A loss to Cheick would have been a pretty bad statement on my career," Mir said. "He was an opponent that I felt I had to come out and decisively smash to make a statement.

"If I had gone out there and won a three-round decision over Cheick Kongo, I don't know think that would have elevated my status."

In the first bout of the pay-per-view event, 6-foot-11 Stefan Struve used his reach and long legs to keep Paul Buentello at bay. Struve used a strategy of leg kicks in the third round to gain a majority decision, much to the dismay of the crowd, which booed the ruling. Two judges had the bout at 29-28, and the third scored it 28-28.

In the much anticipated lightweight fight between Clay Guida and Kenny Florian, Guida sustained a cut to the scalp in the first round, leading to a timeout as the doctor checked the cut before letting the match continue. Midway through the second round, Florian caught Guida with a right hand, sending him to the mat. From there, he pounded on the downed opponent before Guida tapped out on a rear naked choke.

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