Mike Chiappetta • E-mail

B.J. Penn and Sean Sherk say when it's over, they can shake hands and live in peace, but until then, the tension between the two UFC lightweights will continue to build to a boiling point until its inevitable climax at UFC 84.

The two have known each other at least casually, for some time, but things changed when Sherk tested positive for nandrolone following his UFC 73 title defense against Hermes Franca (who ironically also tested positive for steroids). Penn, who regards himself as a fighter above all else, sees the transgression as almost unforgivable, and despite the fact that Sherk was suspended for six months and fined by the California State Athletic Commission, he is taking it upon himself to dole out a real punishment, above lost money and lost time.

"For me, it's hard for me. I've never used performance-enhancing drugs," says the 29-year-old Hawaiian many consider the most talented fighter in the world. "Day in and day out, your body is in pain and you deal with it, so it gets to you when someone else is using performance-enhancing drugs. I feel I'm a purist, the fight is what I live for. I'm more fighter than athlete. When you do those drugs, you take a sport so pure and pervert it. Whether they're doing growth hormone, EPO, blood doping or steroids, it gets to you after a while. I look at fighting and it's the most important thing in the world to me, so I can't take it. I can't handle it."

Sherk, for his part, still maintains his innocence, saying, "I know what I did and didn't do. I went above and beyond what it took for me to be proclaimed innocent. Anyone who followed it knows that. The California state commission knows, too. They cut my penalty in half. I know what I did and didn't do. It's a situation I've dealt with for nine months. There's nothing more I can do."

But despite his words, there will always be some who don't believe him, and Penn is chief among that group of doubters.

Each month before their key events, the UFC hosts a media conference call to publicize the key matchups. Most of the time, they include vanilla discussions of basic strategy and future prospects, but this one took a rare turn as the two took part in a heated verbal exchange.

Sherk was answering a question about the pressure that comes with returning under a cloud of suspicion, and was deflecting the heat on Penn, the current champ.

"What about the pressure of you're not going to be on the juice?" Penn said.

"Yeah," Sherk said dismissively. "No, I don't feel any pressure this time. Come fight night, we'll see."

But Penn wasn't done, becoming more accusatory. "Sean Sherk, did you do steroids?" he asked. "Did you do growth hormone? What about blood doping? If he didn't, he should test at the same level as last time because that's just what he naturally tests at, huh?"

The steroids cloud has been hanging over all of sports for some time now, and with MMA now seeing more coverage than any time in its history, UFC and other organizations will be held under more scrutiny than ever.

Video   MMA Fight Weekly: Penn vs. Sherk Breakdown May 22: Watch the best breakdown of Sherk-Penn you'll find anywhere, plus a double KO you won't believe. NBC Sports

In response, UFC President Dana White recently held a meeting for all of his fighters in which they spoke about several key subjects, including drugs. White has always mentioned the stiff penalties in place by the state athletic commissions, yet for a time, he was so convinced of Sherk's innocence that he contemplated not stripping him of the belt. Eventually, he rethought his position and penalized Sherk by stripping him of the title, which Penn eventually won in a match against Joe Stevenson. But White also took the step of immediately granting Sherk No. 1 contender status.

"Everybody knew where I stood the day it happened," White said. "It's where I stood the entire time. I've known Sean for 10 years, and he doesn't look any different from 10 years ago. I've seen guys go from fat to huge, skinny to big. You see a difference in the body. I've never seen that in him. He's always been a standup, honest guy with me. I've stood by him then, I stand by him now."

Meanwhile, when it comes to the actual fight in the ring, there is only one 100 percent certainty: Sherk will continually look for takedowns. His relentless and willingness to take a hit just to score a takedown lies at the base of his strategy: to take the fight to the ground and to a position he can control.

Sherk is a decent boxer, having improved over time, but he mainly uses his striking to set up takedowns, while Penn has significantly more knockout power in his fists. 

Penn also possesses a great and unorthodox takedown defense, using his balance and flexibility to ward off attempts. He often utilizes a bizarre split-sprawl to defend single-leg takedown tries, or uses his balance to hop on one leg and remain upright while his opponent tries to drag him down. If Sherk is able to take Penn down, it's not easy to keep him on the mat, as he often finds ways to scramble back to his feet. But if Sherk is able to keep him there, Penn is extremely dangerous off his back as one of the preeminent jiu-jitsu practitioners in the sport.

"I don't think he poses any extra threat that anyone else doesn't pose," Sherk said. "I've fought great boxers, wrestlers, jiu-jitsu guys. I think he's strong in every area. I don't see weaknesses in his game. I guess that makes him dangerous. But I have my gameplan, he has his. We'll see who can do it and who the champion is."

Penn is the more dangerous fighter because he has more methods of finishing the fight, but Sherk has built a remarkable record of putting opponents on their back and keeping them there until he scores a TKO or earns a judges' decision.

It's a danger Penn is quite aware of. And he has hinted that instead of Sherk taking him down, perhaps he would be the one looking to take the fight to the ground.

If it goes to the late rounds (remember, title fights are five rounds), conditioning will play a key role. While Sherk is known for infinite stamina, Penn has shown a tendency to get fatigued and fade, losing to Georges St. Pierre and Matt Hughes in fights he was arguably winning early. But "the Prodigy" says he believes he has that problem figured out, having rededicated himself to nutrition and conditioning in the last year.

"All I can do is get into the best shape I can, and do the best I can do," he said. "I did my aerobic, anaerobic, and muscular endurance. I did everything I can possibly do. Different people give opinions. People can say what they want, but maybe this is fight fight people say B.J. got in shape."

Until then, the pressure will continue to build until the two step in the cage and settle their differences the old fashioned way.

"There's something about stepping in, getting it on, and letting it go," Penn said. "After that, I will have said my piece with my actions. After that it will be over."

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