Mike Chiappetta • E-mail

LAS VEGAS - The importance of Forrest Griffin to the UFC can not be understated.

In 2005, with the company betting millions – and ultimately the success or failure of the company – on their new reality show, The Ultimate Fighter, it was Griffin who became a standout personality with a sarcastic wit and humble attitude that turned the stereotypes of MMA fighters on their head and helped draw a legion of new fans.

And it was Griffin’s war with Stephan Bonnar in the first TUF finale that drew millions to the UFC’s first live cable broadcast on Spike, paving the way for its current success.

UFC President Dana White says Griffin "is the American Dream," and declares himself eternally grateful for all the ex-cop has done to help facilitate the rise of the company.

Now, Griffin gets his biggest personal opportunity when he takes on Quinton “Rampage” Jackson for the UFC light-heavyweight championship at Saturday night's UFC 86.

But his biggest opportunity will also be his most challenging.

In Jackson, Griffin faces a champ at the peak of his game. He has explosive hands, an excellent wrestling base, and a battled-tested chin. While most feel that the only decided advantage Griffin holds is his technical jiu-jitsu, he’s faced and conquered the role of underdog before.

Last September, Griffin faced off with Mauricio “Shogun” Rua, a man that many considered to be the best 205-pound fighter in the world, and who holds a first-round KO win over Jackson.

Similarly, in that fight, most experts believed Rua held the advantage in nearly every category. Rua came in with the reputation of an aggressive striker with an endless gas tank and a brilliant ground game. But Griffin used his size to wear him down over the course of the three-round fight, and eventually tapped Rua out with a rear naked choke just 15 seconds from the final bell.

While some dismissed the win, saying that Rua was fighting with an injured knee – even Jackson says “Shogun wasn’t the same guy” – it should also be noted that Griffin fought with a shoulder so damaged that it required extensive surgery soon after.

So, Forrest beat Shogun, who beat Rampage. But what does it all mean? We find out Saturday.

“I don’t care who is the underdog in this fight,” Jackson said. “ That stuff doesn’t matter to me; I don’t gamble and I don’t understand the odds. What matters to me is that I fight a guy who wants to fight.”

Both men are coming off nine-month layoffs to heal respective injuries. Jackson suffered a hand injury during training for his successful title defense against Dan Henderson last September while Griffin's shoulder was a long time coming and a major procedure.

Jackson’s trainer,   Juanito Ibarra, told NBCSports.com that the time off had some benefits for his charge.

“Rampage had been working hard for a while, and this sport takes a toll on your body, so he got a little break,” he said. “He got to spend some time with his family. Did he gain a little weight? Yeah, but that’s okay. He knew how hard he'd have to work to get it off.”

Jackson has the one-punch knockout power than can make it a quick night in the octagon, but Griffin has a decisive reach advantage that, if effective, can keep the champion off-balance and in defensive situations.

“My length plays to my advantage,” Griffin told NBCSports.com. “I’ve got to use the jab, change levels and utilize head movement so I’m not an easy target.”

Griffin, who abhors plane flights and traveling, says he also feels more confident in his approach because he has a kind of home-field advantage. The Georgia native has lived in Las Vegas for the last few years, so gets to sleep in his own bed and keep his usual routine intact.

He also had an addition to his training camp at Xtreme Couture that can pay dividends in game-planning, Wanderlei Silva, who holds a pair of wins over Jackson during their days in Japan’s PRIDE promotion.

Jackson eschews the thought, saying that the fights are far enough in his past (2003 and ’04) that they are essentially meaningless because of his evolution.

“When I was training for Wanderlei, I was training with jiu-jitsu guys,” he says. “And the first time I fought him, I had to fight Chuck [Liddell] 45 minutes earlier [in a tournament]. The second time I fought him, I was whupping his ass until I got caught. Now I have great training partners.”

Jackson shows the hallmark confidence of a champion, while Griffin’s humble roots come through. The two are both marquee fighters with career-defining wins on their resumes, but only one will walk out with the gold.

“It’s the biggest fight of my life,” Griffin said. “I realize that, but I’ve done everything right for it, so I have no doubts and no worries.”

“This is going to be one of the best fights you’ve ever seen, and I do plan on finishing this fight,” Jackson said. “I’m going to be your champion for a long time, and that’s a promise.”

But Griffin loves the role of underdog, has a high pain tolerance and legendary stamina. And for those counting him out, remember the 'American Dream' is fighting on Fourth of July weekend.

"I enjoy being the underdog, proving people wrong, I guess," he says. "There's something about it that brings the best out of me."

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