And now it begins.

Over two wondrous years, Jon Jones rose and rose until he was soaring, gracefully and unimpeded, in the way young athletes of awe-inspiring greatness do when they're building their legends. But now that he has reached the pinnacle of his sport, having won the UFC championship last March, life as a phenom is a thing of the past.

The 24-year-old has arrived. Does he have staying power?

You know what they say about those who've just won championships: You're not a true champ until you've defended the title against a challenge.

Whether Jones looks at his shiny light heavyweight belt in that way or not, he faces a whole new challenge Saturday night when he puts the leather on the line against former champion Quinton Jackson in the main event of UFC 135 in Denver (9 p.m. ET, PPV, $44.99).

By now you've surely picked up on the fact that there's some hype surrounding this "Bones" Jones guy. It all happened so fast. He rolled to a 9-0 record before, remarkably, enhancing his reputation further in a 2009 bout that appears as an "L" on his record. Jones thoroughly battered Matt Hamill that night, gaining full mount before being disqualified for throwing elbow strikes deemed illegal. He then mowed down Brandon Vera and Vladimir Matyushenko, both in the first round. And after dominating the previously unbeaten Ryan Bader in February, he was pegged to replace Rashad Evans in an upcoming title bout against Mauricio Rua. Six weeks later, Jones thrashed "Shogun."

He was the champion. He was Jordan. He was Gretzky. He was the greatest, unmatched and unbeatable.

"Rampage" Jackson has witnessed the buildup surrounding his opponent, and he's not buying into it. "Jon Jones does have skill, and I'm not looking past him at all," he said during a conference call with MMA media on Monday, when he was asked if he considers Jones to be among the sport's top three fighters, pound for pound. "But the only person he really fought was Shogun coming off an injury, and I know that wasn't the real Shogun. Other people can put him up there, but I'm not putting him up there just yet."

Jones had little response to that or even the more cutting remarks thrown out by Rampage during the conference call. "I'm very aware of why I'm here, and it's not to prove I'm a better talker," said Bones. "I'll let him talk and have fun, but I'll demand more respect in the octagon."

Truth be told, he's already getting a good measure of respect from Rampage, even if you have to read between the lines to pick up on it. Like in the quote above, where Jackson said he's not ranking Jones at the top "just yet." Rampage amplified that point in a guest blog he wrote for Yahoo! Sports, saying: "Honestly, I am impressed how fast he's learned. He is the future of the division, in my opinion. But I am the present. Rampage is the present of the UFC light heavyweight division."

That's Jackson's story and he's sticking with it. But here's another perspective on the matter: Bones appears to be the future and present of the division, with Rampage being more of a significant player from its past.

That is not to say Quinton Jackson can no longer fight. It's just that he's no longer living up to his nickname. At 33, Hollywood looks more attractive than ever to the one-time fearsome wrecking machine. In his three most recent bouts -- decision wins over Hamill and Lyoto Machida and a loss to Rashad Evans -- Jackson has been far from aggressive. You might even call him "Lamb-page."

But Jackson does have an incentive to ramp up the intensity this weekend. He has his own legacy to think about. "When I had to fight Machida, I wanted to be the first person to beat him -- nothing against him or anything," said Rampage during the conference call. "I just want to be the first person to beat Jon. Everybody's counting me out and he seems to be underestimating me, so I want to relieve him of his first loss so he can go on to be a great fighter like I know he can be. I just want to give him that first ass-whoopin'."

8: knockouts among his 13 career victories. (Add in his three submissions, and you realize that he's pretty much rendered judges unnecessary.)

6: finishes in his last six bouts. (That includes his DQ "loss" to a battered Hamill.)

11½: reach advantage over Jackson, in inches (an astounding 84½ to a pretty normal 73).

14: knockouts among his 32 career victories.

0: KOs (or finishes of any kind) in four bouts since the end of 2008.

11: film and TV credits since the end of 2008.

What we should expect: Don't be surprised if Jones starts slowly. He's been watching Rampage bring danger since he was in diapers, so he'll be careful . . . until it occurs to him that a long time has passed since his toddlerhood, and that the Jackson in front of him is not as aggressively threatening as the one he used to watch when his parents let him turn on the TV. Once that sinks in, Bones will go on a rampage of his own.

Jackson says he's seen all of Jones's unpredictable moves (spinning fists and kicks, etc.) so many times that they're no longer unpredictable. He misses the point. Even if you know it's in the arsenal, you still need to be quick enough to fend it off when it comes at you. That's easier said than done. And unfortunately for the talk-a-good-game Rampage, success in this fight will be determined by something other than simply what someone says he can do.

Why we should care: The presence of a brass-and-leather belt always focuses the spotlight on a fight. A collision of champions past and present is a worthy storyline. But more than anything, this bout is about legacy. In Jones, we are witnessing the emergence of an athlete who might prove to be the best ever in his sport. In Jackson, we have a guy who, with one punch, can douse all the hype as mere mirage.

What we should not expect: If there's a headbutt or some other foul that results in a momentary pause for a point deduction, there will be no huggy, kissy moment and, despite any animosity that's swelled in the prefight hype, no low-class cheap shot.

"I tell you, it isn't very often that we welcome guests who want to bash each other's brains in. But tonight we do." -- Jimmy Kimmel, introducing Jones and Jackson as guests on his late-night ABC talk show Monday night

"If I've gotta bitch-slap somebody, I'm on it. Whatever I gotta do." -- Dr. Phil McGraw, invited on Jimmy Kimmel Live to sit on the couch with Jones and Jackson and mediate

"It'd be like Spiderman vs. Frankenstein." -- Jones, asked by Kimmel to describe the difference between his fighting style and Jackson's

"I'm the first ever undisputed champion of the sport. I made history already. I'm going to make history a second time by whooping up on him. You gonna be history." -- Jackson, addressing that last part directly to Jones

"Let me help out here. Seriously. I wouldn't take that crap off of him." -- Dr. Phil, asked by Kimmel if "we can talk this out and maybe avoid this fight"

"I hate to see you two go at it like this. I mean, I understand: You're both professionals, you're both fighters, you make your living in the ring, the idea is to beat each other up. But say one nice thing about each other before we go." -- Kimmel

"Quinton, you have such a magnificently large head. Even if my eyes were closed, I'm sure I could just hit you right square in the chin. And, uh, it's just a beautiful thing." -- Jones

"Jon, your ears are not as bad as they appear to be. When I first looked at you, I thought you was the first black gremlin." -- Jackson

What's left? Matt Hughes is a two-time UFC welterweight champion who has won 18 times in the fight promotion, with seven of those victories being title defenses. However, his days as a champ ended five years ago. And if Saturday's bout against Josh Koscheck goes anything like his last one, a 21-second knockout at the hands of B.J. Penn, Hughes's days as a fighter could end as well. Koscheck is a dangerous guy to step into the cage with when your career is on the line.

Perfect opportunity: Travis Browne faced his first big test last fall, fighting Cheick Kongo to a draw. Then, in May, he remained unbeaten by making Stefan Struve his sixth knockout victim in his last seven fights. Now standing in Browne's way is Rob Broughton, who'll never be confused for a tomato can but nonetheless doesn't appear to be a step up in competition. What more must Browne do to show he's ready for a top-tier heavyweight?

Family history: How do you say "Oh, brother!" in Japanese? Four years ago Takanori Gomi had won 13 of 14 fights when he ran into Nick Diaz, who submitted him. (The result was changed to a no contest after Diaz tested positive for pot, his favorite vegetable.). Now Gomi will step in against Nick's little brother, Nate Diaz.

SI Apps
We've Got Apps Too
Get expert analysis, unrivaled access, and the award-winning storytelling only SI can provide - from Peter King, Tom Verducci, Lee Jenkins, Seth Davis, and more - delivered straight to you, along with up-to-the-minute news and live scores.