LAS VEGAS -- Fights become larger than life when two powerful personalities with vastly different backstories face off. And the interest peaks when fans can't figure out which one's going to win.

That pretty much sums up the main event between heavyweight champion Randy (The Natural) Couture and Brock Lesnar at UFC 91 on Saturday night at the MGM Grand Garden Arena (available on pay-per-view).

"Let me tell you what, everybody is very intrigued by this fight," said a giddy UFC president Dana White, who has been bouncing around this week like a six-year-old who has consumed his body weight in M&M's.

Said Lesnar: "Dana and Zuffa and the UFC, they put on fight that people want to see. And Brock Lesnar versus Randy Couture for the heavyweight title is a fight that people are going to tune in and want to see."

Even the Wall Street Journal has covered the pre-fight buildup.

The UFC believes the mixed martial arts matchup will draw 1.2 million pay-per-view buys, a record for the 15-year-old organization. At C$44.99 a shot, that's some $50 million-plus not counting the gate.

There may be a financial meltdown going on worldwide but when two big men with big reputations get in the cage, it seems fight fans are still prepared to dig into their wallet.

The contest pits the 45-year-old Couture, a crafty veteran who has made a career of defying the odds, against the 31-year-old Lesnar, an imposing physical specimen who combines raw power with eye-popping speed and agility.

Stand next to six-foot-two Couture and you feel like you are facing a well put-together athlete who looks younger than his years. Sidle up to the bulky 6-3 Lesnar and it's like meeting a new species.

Couture will be giving up 14 years, at least 50 pounds and some six inches in reach to Lesnar. Plus he has not fought in 15 months due to a contract dispute with the UFC.

Couture dismisses talk of ring rust or the size difference, saying he has spent the last 10 weeks going up against bigger men than Lesnar in training. He says the layoff won't affect him because he spent those 15 months working out with 28 other top pros at his Xtreme Couture gym.

"Each guy brings different things to the table," Couture said. "It's like going to a giant Thanksgiving dinner, you get to try all sorts of things and you learn all kinds of new stuff. That's always been what's exciting about the sport (of mixed martial arts)."

Couture says he has trained smarter as he got older. He changed his diet when he dropped down to light-heavyweight five years ago. And he is always interested in new ways of maintaining his body. This year, that has included a doctor who regularly does his blood work and then addresses any weaknesses with pharmaceutical-grade supplements.

"I think I've just become keener and listened better to my body," he said. "At 45, my body does want to resist some of the things I've tried to put it through. I've got old injuries that want to flare up here or there, a tendinitis here, an ache or a pain there that I didn't have before. But I think you just stay focused and you keep plugging away."

His body shows wear and tear. His misshapen ears would make an Orc cringe. And the veins on his right calf are contorted like a mess of twisted iron rods on a construction site.

Mentally Couture admits he has also changed.

"As I've become more popular and become more successful, financially and otherwise, I've learned and had to become a lot more guarded than I've ever been used to being," he said. "It seems that everybody has an angle, everybody is pitching things and trying to get things from you.

"I've always been a very open, and kind of accepting person and I'm finding that more and more difficult to do, to be how I want to be as we travel down this road."

There have been other costs. His mother was unhappy with some of the revelations in his autobiography "Becoming the Natural."

"That's been the one downside of the whole book process, it's affected the relationship with my mom now, which sucks. And I don't think the book in any way shed a negative light on her. It's just life, it's people's lives and I think that's why people can relate to it. I'm no different that anyone else. And in some way my mom has lost perspective on that."

Lesnar calls Couture a "tough son of a bitch" and a "world-class athlete regardless of age. But he says he has no concerns about the champion. "None at all."

And he says his size will take its toll in the five-round bout

"I've got to push 230 pounds and Randy's got to push around 275 pounds," he said.

Is there a plus being the smaller man? "Well I have to find a way to make that an advantage," Couture said. "For sure, I think I'm a pretty fair athlete myself."

Couture showed in his last win over Gabriel Gonzaga that size doesn't have to matter. He picked up the 242-pound Brazilian and spiked him into the canvas headfirst. Couture landed on top, with Gonzaga's nose being smashed in the ensuring head-on-head clash, unleashing a torrent of blood.

Couture and Lesnar both have stellar wrestling credentials. Couture (16-8) is a former four-time alternate on the U.S. Olympic Greco-Roman team. Lesnar (2-1) is a former NCAA heavyweight champion who went to become a WWE star and earn a tryout with the NFL Minnesota Vikings.

The bookies have been playing it coy. Couture opened as a slight favourite at -125 (you wager $125 to win $100 profit) while Lesnar was plus-105 (a $100 bet earns a profit of $105). The odds have since reversed.

Couture's days with the UFC date back to UFC 13 in May 1997. Lesnar, meanwhile, didn't approach the UFC about joining the organization until UFC 74 in August 2007, when Couture made his last appearance in the cage.

Brain beat brawn the last time Couture came out of retirement. Despite giving up six inches, 13 years, 40 pounds and almost 12 inches in reach, Couture dominated six-foot-eight champion Tim Sylvia at UFC 68 in March 2007.

Couture floored Sylvia seconds into the fight, following up an inside leg kick with an overhand right. Sylvia never recovered and was pummelled for the next 25 minutes.

The Lesnar camp says Lesnar and Sylvia are apples and oranges.

"I think he's just a physically more gifted athlete than Tim Sylvia," said Lesnar trainer Greg Nelson. "Yeah Tim Sylvia has a long reach, he has hard punches too but I think the speed is the biggest difference right there."

Lesnar spent his training camp in the backwoods of northern Minnesota, dreaming up ways to defeat Couture.

"All we had was Randy Couture fights and Randy Couture books to read, so we got to know Randy pretty well," Lesnar said.

He can also draw upon the first-hand experiences of coach Marty Morgan who wrestled Couture three times, beating him in freestyle and losing twice in Greco-Roman.

One question mark is Lesnar's striking. He showed raw power in his submission loss to Frank Mir and bowled Heath Herring over with an overhand right in winning by decision next time out. But he is still learning that side of the game.

"I think Brock's striking is definitely to the point where he's starting to understand really how to apply it, how to use the length of his arms, how to get his body behind those punches and he's getting the ability to be mobile at the same time," said Nelson.

Lesnar says the striking equation is simple: "Speed plus mass equals destruction."

Couture used head movement and angles to negate Sylvia's reach and striking skills. His handlers expect him to do the same against Lesnar.

"We respect Lesnar for his size and his athletic ability," said Shawn Tompkins, Couture's Canadian trainer. "So that means we've got to move and use a lot of angles."

Tompkins believes experience and Couture's edge in striking will be the keys to the fight.

Lightweight contender Kenny Florian is picking Couture to win.

"If he can survive that first round, I really give him a shot at beating Brock Lesnar -- really wearing Lesnar down round after round after round. He needs to be very efficient. While Lesnar has performed very well, he still hasn't been in a championship fight, he still needs more experience.

"So I've got to give the edge to Randy Couture at this point. But I tell you what. At the speed that Lesnar is improving, and with his size and physical skills, he's a threat to anyone. If Randy wins this fight, it's still going to be a battle, start to finish."