Chris Leben caught an early flight out of Las Vegas on a Sunday morning after stopping a previously unbeaten opponent in his last UFC fight. He was back home in Hawaii that night, tucking into a large pizza with his girlfriend.

He awoke to the strangest phone call he had ever received. UFC matchmaker Joe Silva said he wanted Leben back in the octagon in two weeks — two weeks! — to face up-and-coming middleweight Yoshihiro Akiyama at UFC 116.

Leben had never heard of such a brutal schedule, and he knew it could mean disaster. Yet the more he pondered it, he realized he couldn’t resist a remarkable chance to make ironman history.

The shortest turnaround in years for a UFC fighter also was an opportunity for an atoning achievement in a career colored by steroids and legal troubles.

And even if he can’t beat Akiyama on such short notice, Leben would have hated himself for not trying.

"I knew all the reasons I shouldn’t do it, but I remembered that I’m a fighter, and they’re presenting me with a great opportunity," Leben said. "I couldn’t pass up the chance. My goal is to go as far as I can go in this game. If you’re not shooting for the top, you’re in the wrong sport. This is really going to kick-start my career, really put me up in the elite division."

Before heavyweight champion Brock Lesnar fights interim champ Shane Carwin at the MGM Grand Garden tonight, Leben and Akiyama will meet in perhaps the most improbable co-main event in recent UFC history, pitting a Japanese judo champion with little stateside fame in his second UFC fight against a guy who just fought two weeks ago.

Leben (20-6) beat Aaron Simpson in his last bout, but said after the fight that he wouldn’t mind four to six months off before his next fight. He gave up that hope when the UFC chose him to replace Brazilian veteran Wanderlei Silva, who dropped out of his fight against Akiyama with an injury on June 22.

The more Leben thought about the opportunity, the more he liked it. He had only a few cursory bumps and bruises from his surprising win over Simpson, and his training camp leading up to the fight already had him in top shape.

"The thing about our sport is, it’s not like football," Leben said. "You don’t have to study your opponent a ton. There’s a few key things, but other than that, my job is to oppose my will on my opponent, not plan for what he’s going to do to me, so I wasn’t worried about preparation that way."

And after a rocky career that has included a nine-month suspension for a positive steroids test in 2008, jail time for a probation violation, and other legal troubles, Leben was eager for another chance to show he has turned around his life.

Leben believes his technique and his life have improved markedly since moving from Portland, Ore., to Hawaii, where he runs the Ultimate Fight School on University Avenue. Leben’s training team embraced the challenge presented by the turnaround — and coach Burton Richardson was grateful his fighter took relatively little punishment in beating Simpson.

"We looked at it like the Simpson fight was a really hard, high-intensity sparring session," Richardson said. "Now, we’ve just bumped it up a little more."

Akiyama (13-1) was a judo gold medalist in the Asian Games before joining the K-1 promotion in his native Japan. Akiyama’s debut at UFC 100 last July went this distance for the first time in his MMA career, but he earned a split decision over Alan Belcher despite breaking an orbital bone in his face.

He hasn’t fought since then, and he nearly declined the chance to face Leben after Silva dropped out. Akiyama had turned down other fights in the past year because he wanted to fight Silva, but eventually decided to go through with the replacement fight, even after indirectly criticizing Leben for an unimpressive record.

Yet Leben has put together a solid, workmanlike career after appearing on the debut season of "The Ultimate Fighter," the UFC’s reality television show, where he created a memorable impression with his wisecracks and cockiness — and by punching through two doors in the fighters’ house after two contestants pulled a prank on him.

Leben knows if he can pull off another upset tonight, he’ll be known for much more than his misdeeds.

"I figured I just needed to buckle down for another couple of weeks, and then I’ll know," Leben said. "My body is definitely beat up, but I’m ready."