Randy Couture already overcame bigger obstacles than 265-pound Brock Lesnar just to get into the octagon at UFC 91.

Couture has heard every reason he'll struggle to defend his heavyweight title on Saturday night. If it isn't his age, it's his recent inactivity. If it isn't Couture's many pursuits outside mixed martial arts, it's his disappointment from failing to land his dream bout against Fedor Emelianenko.

They're all legitimate concerns, Couture agrees. But even at 45, with a decade of memorable fighting behind him and a bright career as an actor looming when he finally leaves the sport, Couture doesn't see any real reason he can't remain his sport's most decorated heavyweight for a while longer — even against the fighter widely thought to be the next great one.

"I'm here for the love of the sport," Couture told The Associated Press in a phone interview after yet another two-hour workout at his gym in Las Vegas. "Everything else that the sport has brought me is nice, but I still feel like I'm getting better, and physically still capable of doing this.

"If I wasn't withstanding the training and measuring up with my training partners, it would be another thing," Couture added. "People have been talking about how sharp I'd be after taking the year off, with a book tour and a movie, and those were all positive things that took me away from training, but I learned a lot of things."

Couture is returning to action after a 15-month layoff during a contract dispute with UFC. The sport's dominant promotions company never stripped its biggest name of his title belt, and they eventually resolved their differences fairly amicably.

Couture realized every month counts when a fighter is in his mid-40s, so even while he was away from the big stage, he never left the sport. Whether on a movie set or back at home, Couture put in hundreds of hours in the gym, staying in fighting shape for his entire layoff.

"I've never been one to sit around," Couture said. "I like to train, I like to be in the gym. Everybody asked about ring rust. I just don't think it's the same for mixed martial arts as it is for boxing. The stuff we do in training is almost as tough on us as the fight."

When he returned to the UFC fold, the company immediately matched him against Lesnar, the former NCAA wrestler and pro wrestling star who tried out for the Minnesota Vikings before falling in love with MMA. Lesnar has taken a few halfhearted pokes at Couture's age and inactivity, saying he couldn't imagine how Couture wouldn't be rusty at the MGM Grand Garden.

"I ain't buying nothing from a 45-year-old guy that's been fighting for 12 years," Lesnar said. "I think it'll probably (affect) him, but he might not admit it until it's over."

Couture improved himself in several ways during his absence from the octagon, with everything from a change in his boxing style to regular lessons from a West Hollywood acting coach. With seven films under his belt, including the titular role in the recent "The Scorpion King 2: Rise of a Warrior," Couture has positioned himself for success outside MMA, even though his services still will be in demand as a commentator whenever he's done fighting.

"I'm interested in being challenged," Couture said. "I don't just want to play fight roles. I can do that with my eyes closed. We'll just have to see and make smart choices and continue to learn."

Couture still dreams of taking on Emelianenko, the feared Russian fighter who has been tied to several promotion companies in recent years, most recently Affliction. The bout would be the logical summit for one of the sport's most successful careers, but the morass of contractual obligations and head-butting promotions companies probably will force Couture to write another ending.

"I'm still hopeful that it'll work out, but I realize that time gets shorter all the time," Couture said. "I'm pretty realistic. It's probably not going to happen. It's probably better than a 90 percent chance it's not, and I'm OK with that. Six months ago, I probably wouldn't have been. Now that I've got a better understanding of the contracts and everything, toiling away and spending money frivolously isn't going to make it happen.

"It's a waste of time and energy. I'd rather fight guys like Brock."