Photo Gallery: Sports Extra: Penn vs. Diaz

Photo Gallery: Sports Extra: UFC 137 Prelims

With his left eye swollen shut, B.J. Penn may have closed the door on a legendary mixed martial arts career.

One of only two men to hold world titles in multiple weight classes, Penn said Saturday night that this was his last fight following a unanimous-decision loss to Nick Diaz in the main event of UFC 137 at the Mandalay Bay Events Center in Las Vegas.

After the fight, Penn told UFC color commentator Joe Rogan in the cage that he might be finished.

"You know what, I got a daughter, I got another daughter on the way; I don’t want to go home looking like this," Penn said. "I’m done."

And with that, Penn, who has hinted at retiring before, left the cage after a bloody loss to Diaz.

Both fighters were beaten badly as the fight mostly consisted of Diaz landing significantly more punches standing against Penn, who was never knocked down in the fight.

Penn opened as a slight favorite over Diaz and started Round 1 with an immediate two-punch combo to take the center of the cage.

Penn outboxed Diaz in the first round and at one point nearly took Diaz’s back when the fight hit the ground.

From then on, Diaz took control as Penn started to tire midway through the second round. Diaz controlled the round impressively enough that one judge gave him a 10-8 round.

Diaz again won the battle standing in the third round, but Penn made it a fight, testing Diaz’s chin multiple times as both fighters kept their hands down.

Two judges scored the contest 29-28, while the third had it 29-27, all in favor of Diaz, who has won 11 fights.

Diaz, who was originally supposed to challenge Georges St-Pierre for the welterweight title, called out the champion after the fight.

"I don’t think Georges is hurt, I think he’s scared," Diaz said.

St-Pierre’s title defense against Carlos Condit, who was Penn’s originally scheduled opponent, was canceled early last week when St-Pierre pulled out with a knee injury.

Diaz improved his record to 27-7, with his 11th consecutive victory, while Penn dropped to 16-8-2 overall.

Penn had to be taken to the hospital after the fight and did not attend the post-fight press conference.