LOS ANGELES (AP) — When Anthony Pettis steps back into the octagon at UFC 181, the flashy lightweight champion will be in just his fourth fight in more than three years. Although he is one of mixed martial arts' top talents, Pettis hasn't even seen a second round since October 2011.

Gilbert Melendez intends to make Pettis regret all of his injuries and inactivity in a title fight that could serve as the masterwork of his long career.

"There's nothing left to accomplish except this," Melendez said this week. "If I can do this, I feel like I'm one of the greatest of all time."

While Pettis (17-2) hopes to begin a long reign as one of the UFC's top stars at the Mandalay Bay Events Center in Las Vegas on Saturday night, Melendez (22-3) relishes the chance to take the champion into areas he hasn't visited in years. While Melendez's big right hand is his greatest strength, he believes he can also win a mental matchup with the champion.

"It'll get real interesting when we get out of the first round and he hasn't hit me with any of that spinning stuff," Melendez said. "What's he going to do when we're in a fight?"

Melendez's shot at Pettis is the penultimate event at UFC 181, a rare card featuring two title fights. Welterweight champion Johny Hendricks returns from a long layoff for his own first title defense in a rematch with Robbie Lawler. The card also features two heavyweight bouts and popular bantamweight Urijah Faber.

But the MMA world has been anticipating Pettis' return to the cage for 16 months, ever since he claimed the belt with a first-round submission victory over divisive champion Benson Henderson.

Pettis' incredible athleticism makes him a highlight-reel staple — never more than in December 2010, when he jumped off the side of the cage to flatten Henderson with the now-famous "Showtime" kick in their first meeting. Pettis can't deny his absence hurt, but he's eager to make up for lost time, perhaps fighting four times in the next year.

"I won the belt, but then I was off for a year," Pettis said. "I can't consider myself the best of the best until I prove it for about a year. That's what I want to start this Saturday night."

Pettis' fame has grown even during his absence from the octagon. Along with several endorsement deals, he is the first UFC star to appear on a Wheaties box, which was unveiled in Las Vegas on Thursday. Pettis wears a shirt and tie on the box, the lightweight strap hanging over his right shoulder.

Yet the Milwaukee native wasn't an instant star in MMA, and he realizes how quickly his success can disappear with a loss. He respects Melendez's striking, but believes he can counter it with a well-rounded game.

"I've been calling a first-round knockout, and I'm still going for it, but he doesn't drop easy," Pettis said. "If it doesn't happen, I'm prepared to go five rounds. He's one of the best guys in the sport, but I'm going to show everybody what I'm all about if they've forgotten."

Melendez already got a UFC lightweight title shot in April 2013 after dominating the weight class in the Strikeforce promotion. The San Francisco-based fighter made it through five tough-to-score rounds against Henderson, but lost a razor-thin split decision in the Bay Area.

When Pettis took the belt away from Henderson last year, Melendez knew he had another shot at the title. Still, he had to wait: Pettis tore a ligament in his knee and recovered gradually from the surgery.

Melendez passed the time by commentating on ESPN, and he agreed to coach the UFC's new women's strawweights opposite Pettis on the current season of "The Ultimate Fighter," the promotion's long-running reality show. The foes barely interacted during their six weeks on the show, preferring to save their enmity for UFC 181.

"I didn't want to get to know him," Melendez said. "I don't have a problem with him, but that's not what I want. I want to beat him up and take his belt."