Diaz and Penn were given Fight of the Night honors at UFC 137 at the Mandalay Bay Events Center for their three-round slugfest in the main event. Diaz and Penn each got bonus checks for $75,000 for their performances in the fight, which Diaz dominated in the standup game for a unanimous decision win – and prompting Penn to announce his retirement.
Also picking up bonus checks for their performances were Donald Cerrone for Submission of the Night and Bart Palaszewski for Knockout of the Night. Cerrone's submission was the only one on the 11-fight card.
Penn was the clear fan favorite early in the fight, but as Diaz continued to pepper him with shots to the face, the crowd seemed to turn in favor of Diaz – or at least in favor of hoping to see an exciting finish after seeing seven decisions leading up to the main event.
Though Diaz couldn't finish the two-time UFC champ, he left his face battered and bloodied. After the fight, Penn said the fight would be his last.
"It's probably the last time you're ever going to see me in here," Penn told Joe Rogan. "That's it. I've got another daughter on the way – I don't want to go home looking like this."
Diaz, who was supposed to face Georges St-Pierre for the welterweight title on the card until he was removed from the fight for missing two press conferences, now is back in line to likely face the winner of St-Pierre vs. Carlos Condit. That fight won't take place until St-Pierre recovers from a knee injury suffered in training earlier this month.
"It feels good to be back fighting," Diaz said. "In the second round, I turned it on and tried to take him out. He started going on defense in Round 3. Things would have been different if there were five rounds. I would have taken him out for sure in the fourth. BJ is one of the best there is, and not that many would go out there and take all those punches."
Cerrone continued his blitz up the UFC's lightweight ladder, submitting Dennis Siver with a first-round rear naked choke. That win gave Cerrone six straight and four straight in the UFC – all in 2011 after moving over from the WEC. Siver's four-fight winning streak was snapped with the loss.
Palazewski was the card's biggest underdog winner. Fighting in the UFC for the first time, and back in action for the first time in 10 months, Palaszewski stunned Tyson Griffin with a hook, then battered him with lefts and rights until one big right put Griffin on the canvas.
After the fight, Palaszewski, a former WEC and IFL standout, said he believes he broke both of his hands landing the shots that ended the fight.