Little stability at heavyweight summit

UFC heavyweight champion Junior dos Santos is unequivocal in the belief that Saturday's title defense in Las Vegas against Frank Mir will be his first of many.

History, however, suggests otherwise.

"Anything can really happen at any moment," said Cain Velasquez (9-1), who dropped the title in his first defense last year after dos Santos clocked him behind the ear.

Since its inception in 1997, UFC's heavyweight strap, the promotion's longest-running championship, has passed between fighters with alarming regularity. Of the 15 men to grab hold of the title (including interim belts) only four -- Randy Couture, Andrei Arlovski, Tim Sylvia and Brock Lesnar -- have defended it more than once.

Their best streak? Two straight.

"It's always been a particularly volatile weight class," said Couture, who retired last year as the only three-time heavyweight champion in UFC history. "In MMA there are so many ways to lose, and those guys are so big, it really only takes one punch [to end a fight]. With a guy who is 230 pounds and up, using 6-ounce gloves, it's easy to end your night."

Compared to boxing, which features heavyweights like brothers Vitali and Wladimir Klitschko sustaining prolonged runs at the top, Couture suggests MMA's flip-a-coin reality is "good for fans and good for the sport."

Couture, true to his word, favors Mir (16-5) to beat dos Santos (14-1) in the UFC 146 main event at the MGM Grand Garden Arena, a sentiment that has gone unshared by oddsmakers and the general public.

While the merry-go-round nature of UFC's heavyweight title is undeniable, there are those who disagree with Couture's assessment.

Boxing reached its greatest heights when the public embraced dominant heavyweights facing difficult challenges.

Would that not also be true of mixed martial arts?

Javier Mendez, the respected trainer of Velasquez and Strikeforce heavyweight grand prix victor Daniel Cormier, says yes.

"If there was a heavyweight that could sustain it, I think it would be great for the sport," he said.

In Velasquez, Mendez thought he had a transformative Jon Jones-type fighter. He wasn't alone. Couture also viewed the 29-year-old Mexican-American, who knocked out Lesnar to claim the belt, as someone who would plant himself atop the division. But all it took was one heavy shot from dos Santos for Velasquez's title run to end in less than 60 seconds.

"I think heavyweight is the most dangerous division," dos Santos said. "There's too much power involved. When you get punched by a heavyweight, you are in trouble. That's why I think it's so hard to keep the title."

There is also the promotion's heavyweight renaissance to consider. During the middle part of the last decade, a period UFC president Dana White bemoans for its lack of talent among the class, the top heavyweight, Fedor Emelianenko, engineered a string of victories that could be considered unimaginable in the Octagon.

The Russian deserves credit for winning, of course, but he was also aided by beneficial matchmaking. There's no such respite for today's crop of UFC contenders.

Eight of the top 10 MMA heavyweights currently reside in the UFC, according to ESPN.com's rankings. Zuffa, which owns and operates UFC and Strikeforce, focused on rebuilding the division after lean years when Sylvia and Arlovski went back and forth.

Said Mir: "I do think it's as deep as it's ever been."

That suggests more parity is on the way.

"Now they're not just big guys," Couture said. "They can move. They can wrestle. They can grapple and have good submission skills. They're just well-rounded, good fighters.

"I get tired of the shoo-in, the guy you say 'Oh yeah, he's going to win another one.' It's like the Anderson Silva deal. You kind of get tired of it. At the end of the day, you know the guy he's fighting isn't going to be able to touch him. I'm way more intrigued in a very competitive fight where I can see it going either way."

Silva's dominance propelled him to the top of the sport's pound-for-pound rankings. With nine consecutive middleweight title defenses, "The Spider" is widely considered the sport's finest fighter. There is undeniable value in prolonged success.

Save the heavyweight division, UFC has, for the first time really, entered into an era of dominant champions.

Silva stands alone. Following six consecutive welterweight defenses, Georges St. Pierre is a close second. Jones stabilized the light heavyweight division last year and has defended the title three times. Jose Aldo has made featherweight his playground. And 135 pounds features the confounding puzzle that is Dominick Cruz.

Only heavyweight and lightweight, where the newly crowned Benson Henderson out-pointed Frankie Edgar last year, have yet to join the party.

Mir, the 32-year-old challenger -- a two-time titleholder who relinquished the belt each time sans a defense -- is of the opinion that a similar fate awaits the Brazilian slugger.

And history is on his side.

But then again, dos Santos could be cut from a different cloth.

"I really believe I can keep this belt for a long, long time," said the current titleholder. "My dream was to become champion and now I'm champion. Now I want to break records. I want to keep this belt for a long, long time and be part of the history of the heavyweights."