LAS VEGAS - The take on George St. Pierre's last opponent, Jon Fitch, was that while Fitch was good, St. Pierre was better.

"I think honestly that I'm better than he is in every single aspect of the game," the UFC welterweight champion said before proving it in a lopsided five-round decision at UFC 87.

St. Pierre can't say the same this time, with lightweight title-holder B.J. (The Prodigy) Penn on the other side of the cage Saturday night at UFC 94 at the MGM Grand Garden Arena (available on pay-per-view).

It's champion against champion, with a place in mixed martial arts history on the line. Each fighter has skills that cancel the other's out.

"They're pretty evenly matched," acknowledged St. Pierre trainer Greg Jackson. "B.J. has very slick submission stuff but Georges has great submission defence. You know what I mean? You can go back and forth all day with it."

Penn (13-4-1) is a fighting phenomenon who has added stellar standup skills to a world champion jiu-jitsu base. His takedown defence is among the best in the business, partially because of his extraordinary balance and agility. A cross between Gumby and Stretch Armstrong, the five-foot-nine Penn can make like a pretzel during a fight if needed.

"To be honest with you, I think B.J. could have played in the NBA if he wanted to, he's that talented," said UFC president Dana White, only half-joking.

Penn weighed in at 168 Friday while St. Pierre was 170 before a packed crowd at one end of the arena.

Penn likes to come out of the gate fast and, with his superior striking skills, can do damage quickly. The 30-year-old from Hilo, Hawaii, busted Joe Stevenson open from the get-go at UFC 80 and used his fists to batter Sean Sherk at UFC 84.

St. Pierre (17-2) is a physical specimen who also comes to the cage with a well-stocked tool kit.

"St. Pierre, you know, he's an animal," said former UFC lightweight champion Jens (Lil Evil) Pulver. "There's nothing you can say negative about the guy. He's a tank, a wrecking machine."

The 27-year-old from Montreal has made himself into one of the most effective wrestlers in mixed martial arts, taking down former all-Americans almost at will. Until he was summoned as an injury replacement for Matt Serra against Matt Hughes at UFC 79 in December 2007, he was preparing for a run at the Canadian Olympic wrestling team for Beijing. "Would he have made it? It would have been difficult but possible, yes," said coach Firas Zahabi. "Because of his athleticism, yes."

He recently earned his black belt in jiu-jitsu and has a strong standup game, with a good array of kicks.

Striking could hold the key to the outcome Saturday night. If Penn can back St. Pierre up as he did in the first round the first time they met (St. Pierre won a split decision at UFC 58 in March 2006), he could impose his will on the fight.

Penn has already turned heads in the boxing world with his striking ability, according to White.

"Out of all the boxing guys that me and Lorenzo (UFC co-owner Lorenzo Fertitta) know and talk to all the time, he's the only (UFC) guy that they respect his hands," he said. "The boxing guys say `That kid could box, he's got good hands."'

But boxers also compliment St. Pierre.

"He's not a boxer but he can fight," said Olivier Lontchi, a top-10 ranked super-bantamweight who has sparred with St. Pierre. "He's big and he's smart. I joke with him sometimes that he should quit extreme fighting and come and box. I have trouble with him sometimes and he's not a boxer. He's good. He learns fast."

While Penn says the edge between the two fighter's standup game is close, he adds: "I think I can hit him and hurt him, you know what I mean?"

So if their skills largely cancel each other out, what factors will determine this fight?

As in any MMA contest, one punch or mistake could be the beginning of the end. But conditioning, game plan, mental toughness and desire will all play their part.

Penn's conditioning improved notably when the UFC asked him to go back down to 155 pounds. He is returning to 170 pounds to meet St. Pierre, looking to win the welterweight title for a second time.

But while Penn -- who normally walks around at 170 -- looked chiselled as a lightweight, coach Rudy Valentino said he was actually weaker at 155 because of the weight cut. Penn himself says he feels better at 170.

Under the tutelage of strength and conditioning coach Jon Chaimberg, St. Pierre is a physical beast.

"He's the most powerful I've ever seen him. ... They'll be no match in strength, I can promise you that, and in conditioning, they'll be no match," said Chaimberg.

St. Pierre, who stands 5-10, will be bigger. He could outweigh Penn by more than 15 pounds Saturday night, given his weight cut.

Penn downplays that size difference.

"It's just me and him and everybody can be broken. I'm going to attack his central nervous system, I'm going to attack his heart and we're going to take it from there. As soon as we lock up, it's going to feel like we're the same strength, it always does when I fight with somebody."

Penn's body at 170 appears pudgy compared to St. Pierre's rock-hard physique -- the Canadian was recently featured on the front of Men's Fitness magazine. But Jackson, for one, is expecting Penn to arrive in shape.

"We're expecting conditioning to not be a factor and for Penn to come in like a freight train and try to take Georges out."

St. Pierre's goal will be to blunt that attack, to force Penn to rethink his strategy.

"That's the cornerstone of every game plan, is to take them out of their comfort zone and make them fight your fight," Jackson added.

The Canadian could do that by taking Penn down, using lateral movement, frustrating him with kicks, using his reach to keep him away with jabs.

Penn will be looking to resist the takedown -- "We know Georges gets real comfortable if he can get that takedown and control where he wants to fight." -- and hurt St. Pierre with his fists so he can take the Canadian to the canvas.

"Sooner or later Georges is going to end up on his back as the fight goes on," Penn promised. "He's not a guy that ends up on his back too often. And that's when I'm going to start doing damage."

As to game plans, Penn's approach to fights -- and St. Pierre -- is simple.

"I just prepare on the thing I do and what I'm good at. And try to take those techniques and just shove them down his throat actually."

St. Pierre has a master tactitican in Jackson overseeing strategy. St. Pierre is a good student, so the plan should be executed to perfection.

"If he loses, it's just going to be a bad night," Jackson said. "Otherwise he's set up a structure that is going to enable him to win."

St. Pierre has been relaxed and confident coming into the fight. Reporters who cover the Canadian regularly can reel off strings of GSP-speak, motivational sentences that seem straight from the lips of a sports psychologist. But he has largely ignored the cliches this time, speaking from the heart about why the fight is so important to him.

The normally ultra-relaxed Penn has been more serious, but equally committed.

Penn comes into the bout a father, with a baby daughter back home. Valentino says the new addition has been a positive, rather than a distraction.

"When you're young, you just run around and have fun. I think by having a family now, he's become more focused and more grounded, knowing what he wants in the fight world right now."

Like St. Pierre, Penn is fighting for legacy and bragging rights. He can also become the first UFC fighter to hold championships in two weight classes at the same time.

Both men have already made bags of money from the sport.

St. Pierre, according to one source, got a cheque for US$500,000 when he won the title at UFC 65 in November 2006. His future is already well taken care of. After his last fight, he paid off his parents' mortgage.

"It was a dream for me to do that," he said.

Signature T-shirts from Silver Star Clothing (www.buysilverstar.com) are the latest addition to the growing GSP empire. And if you are so inclined, you can buy a limited-edited giclee portrait of the fighter by artist Brian Fox (www.gspfightclub.com).

Penn recently went past the 50,000 mark for members of his website, www.bjpenn.com which offered a variety of travel packages for Hawaiian fans to come to the fight. He has a radio show and TV show in Hawaii with hopes to take it national.

The UFC expects a bumper audience for the fight, showcasing it on Super Bowl Saturday.

"It's the biggest weekend in Vegas, bigger than New Year's Eve. It's bigger than anything," said White.

"You know how pumped up other fighters are for this fight? he added. "This is like a fight that fighters wants to see. That's when you know you've got a great fight."

Former middleweight champion Rich Franklin sees pluses on both sides, starting with Penn's striking.

"His timing with his striking has really impressed me recently and you never really consider him a striker," he said. "With that being said, GSP's wrestling is phenomenal, he's one of the most well-rounded fighters in the UFC, I'd say. But with B.J. being the way he is, all flimsy and flexible and unorthodox with his jiu-jitsu, that kind of plays into a bad game plan for GSP. So he's going to have to come up with some kind of tricky game plan. But he's a champion and that's what champions do."

Fitch, for one, will be rooting for St. Pierre. He knows if Penn wins, there will be a logjam for contenders as the Hawaiian defends both titles.

"I can't really like pick the fight. All I can say is for convenience sake, I really want GSP to win just because it's more convenient for the rest of the welterweights and the rest of the lightweights in the world who are waiting for a title shot."