It's tough to blame B.J. Penn for leaning on a mental crutch to get him through those first few minutes of physical peril in the octagon with Georges St. Pierre.

In the days leading up to their heavily anticipated title bout at UFC 94 in Las Vegas, Penn has improbably proclaimed that the UFC welterweight champion is a quitter who won't have anything left if Penn can just survive the initial onslaught of arguably the best pound-for-pound mixed martial artist in the world.

"That's how I'm going to beat him, because I'm going to get through all of his skills," Penn said. "You know he's tough and he's all of these things, but once I get through, he's going to be empty on the inside, and that's how I'm going to finish him."

St. Pierre (17-2) might be the favorite in the MGM Grand Garden's rematch of the two top UFC stars' memorable March 2006 bout, but Penn (13-4-1) is far from a one-in-a-million underdog after winning the UFC lightweight title early last year and defending it last May.

"I love to be the underdog," Penn said. "I haven't been the underdog for a long time. Fighters who don't believe I can win this fight, it's simply because they don't believe in themselves, that they could go out and beat a great champion at a higher weight."

With a new dedication to training, Penn has been good enough in his recent fights to make the matchup an entertaining cap to a remarkable three-month run for UFC under the Vegas lights, following Brock Lesnar's heavyweight title victory in November and Rashad Evans' win over Forrest Griffin last month.

Some veteran MMA observers think St. Pierre-Penn is the best bout in the sport's history, pitting two elite fighters at the peak of their talents. They've been featured on a three-part reality television show dedicated to their preparations for the bout, and UFC president Dana White predicts the most pay-per-view buys in the sport's history.

"You're lucky if you get to see three or four of these types of fights in your lifetime," White said. "Two of the best fighters in the world in their weight classes, both champions facing each other both in their prime. ... This fight is a Hagler-Hearns. This fight is Hagler-Leonard."

With a victory over St. Pierre, Penn would be the first fighter to hold UFC titles simultaneously in two weight classes. But St. Pierre has only lost to former champions Matt Hughes and Matt Serra, and the Montreal native beat Penn by a memorably contentious split decision in their first fight nearly three years ago.

"It's like when you play cards," St. Pierre said. "You don't show your hand. I've been studying a lot of tape. He's a very well-rounded fighter, and that's why he's so good. On the other hand, I think I have the answer to that problem. I don't have a specific thing that I'm going to beat him with. I have a game plan, and I'm going to stick to it."

The bout could hinge on Penn's ability to stop St. Pierre from taking him to the canvas, where he's finished off many opponents with his strength and technique. St. Pierre's wrestling prowess is well-known to Penn, who was taken down in the second and third rounds of their first bout, so Penn spent his training camp honing his own impressive defenses against St. Pierre's desire to fight on the floor.

"He's going to try to kick me hard," Penn said. "He's going to try to punch me hard. He's going to try to slam me on my head. ... When he realizes he can't get that takedown, then he's going to realize he's in a fistfight, and then he's going to realize who he's going up against."

Penn hasn't fought at 170 pounds since September 2006, when he lost for the third time in four fights at 170 or 185. The Hawaii native attributes those failures to poor training, not physical weakness, and promises he hasn't made such preparation mistakes for St. Pierre.

Penn, the first American-born man to win a world jiu-jitsu title, thinks he wasn't nearly at the peak of his abilities when he lost to St. Pierre nearly three years ago. Like Rampage Jackson, Penn claims he has only recently begun to tap his true potential, swearing off drinking and partying for a life of proper conditioning, diet and coaching.

"I definitely wasn't working as hard," Penn said. "I didn't have the drive. I was just kind of inching by, and just getting through fights and getting through life.

"He's good at everything, and I don't have a specific technique that I'm going to beat him with," Penn added. "I'm just going to beat him with my mind and with my heart."