Trainer Greg Jackson knew something was wrong with Georges St. Pierre before the fighter even stepped into the cage.

"He was too nervous, he was looking around for people to reassure him," Jackson said of the UFC 69 bout against Matt Serra in Houston.

Three minutes 25 seconds later, a dazed St. Pierre was on his back, and Serra was the UFC welterweight champion in one of the biggest upsets in recent mixed martial arts history.

The two go at it again Saturday night at UFC 83 at a soldout Bell Centre in the UFC's Canadian debut. Those close to St. Pierre say the 26-year-old Quebecer is fit, focused and extremely motivated.

"He's real hungry, and that's the key to a fighter," Jackson said. "If they're not hungry, if they've already eaten too many meals, you shouldn't fight. You should wait until you're hungry again. That's the real key with Georges. If he wants it, then he's going to win.

"That first Serra fight, he didn't want it. He just wanted to get in, do his job and get out. He didn't want to beat the guy. You've got to want to beat the guy, you've got to be hungry."

St. Pierre was anything but last April. He had won the title five months earlier at UFC 65, ending Matt Hughes' run.

Then St. Pierre lost the plot. His father was seriously ill. A cousin was in a coma after a car accident. There were injuries. He lost focus.

St. Pierre (15-2) has been all business since, dispatching Josh Koscheck and Hughes (for a second time). The champion, meanwhile, has been out of action _ first because of TV duties as a coach on "The Ultimate Fighter" reality TV show and then because of two herniated discs.

Still, the 33-year-old Serra (16-4), a jiu-jitsu black belt, is able to make opponents pay with a submission hold if they leave a limb dangling.

"I'm not trying to be vain. but I feel good about the fight," he said. "Everybody's kind of looking past the last fight, thinking like 'Oh, that wasn't the real him.' I mean it looked liked him," he added. "I don't know, was it his freaking stunt double? It was him, I'm telling you."

And Serra said he believes his hedgehog-like jiu-jitsu will slow St. Pierre down. And if St. Pierre wants to throw, the 5-6 Serra will punch right back, despite giving away four inches in height and a considerable reach advantage.

"If the fight goes downstairs, I'm going to be prepared," Serra said. "And upstairs, I'm feeling very very comfortable now. So my realm is not just going to be on the floor, it's going to be everywhere."

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