Penn grows up, awaits Diaz in UFC 137

A calm and mature BJ Penn is preparing to fight a brash and often rebellious, yet incredibly talented fighter in the main event of UFC 137 on Saturday.

Penn is scheduled to take on Nick Diaz, and the description of Diaz could just as easily be applied to the Penn of nearly a decade ago.

Now 32 and the father of a 2-year-old daughter, Penn attributes his toned-down demeanor to simply growing up.

"I'm going to step in the cage and be as violent as I can, but with the other stuff, I'm getting too old, man," he said at a workout in Las Vegas on Wednesday, in advance of his welterweight bout against Diaz at Mandalay Bay.

Diaz, 28, is mixed martial arts' resident bad boy, a title once bestowed upon Penn, who early in his career often butted heads with the Ultimate Fighting Championship and UFC president Dana White in particular.

While Penn refused to rip Diaz, he said he would offer some blunt advice to himself if he could go back in time.

"Shut your mouth, because what you say doesn't really matter," he said. "It only matters if you win."

Penn has done plenty of winning in his career. He has been a champion in two weight classes and is still one of the most popular figures in the sport. He entered the UFC at just 22 and has accomplished almost everything possible in MMA, which is probably why he already faces constant questions about retirement at age 32.

Trainer Jason Parillo said Penn is still motivated to continue his career.

"I believe he's fighting to show people he's a legitimate welterweight and he can compete at the highest tier of the division, and that he's one of the best fighters that's ever walked," Parillo said.

Penn said he just loves the challenges -- and pay -- the sport can provide.

"I'm probably addicted to the attention, and it's a job. I get a paycheck," he said. "But I still love to fight, When people say, 'Hey, that guy's pretty good. There's no way you can kick his ass.' I say, 'Let me try.' "

He will attempt to beat Diaz, a former Strikeforce champion who returns to the UFC on a 10-fight winning streak outside the organization.

Penn said a win over such a challenging opponent would mean a great deal at this stage of his career, even with no belts on the line.

"It would mean I'm still here. I'm still going. I'm still one of the best fighters in the world," Penn said. "I guess words can't explain it."

He calls Diaz the best boxer in MMA, but he thinks the respect between the two might keep Diaz from utilizing one of his best weapons, an ability to frustrate opponents into a brawl with taunting and trash-talking in the cage.

Even if Diaz tries that, Parillo said all that growing up outside the cage could benefit Penn inside it.

"I believe with how emotional a guy he is, he could have easily been suckered into Nick's games in the past with the taunting and all of that, but I think there's been some maturity with BJ over the course of time," Parillo said. "He knows what he needs to do. He's been at the top of the mountain, and he's felt like he's been in a valley before. I think all those experiences are going to help him not get suckered into some kind of BS (trash)-talking."

Contact reporter Adam Hill at ahill@reviewjournal.com or 702-224-5509. Follow him on Twitter: @adamhilllvrj.