Fighter has a lot to prove

The last time Nate Diaz stepped into the octagon, he emerged as winner of Season 5 of the Ultimate Fighting Championship's reality show "The Ultimate Fighter."

It didn't prove to be the crowning achievement he had hoped for, however.

After losing the first round, Diaz won by submission when Manny Gamburyan suffered a severe shoulder injury when attempting a takedown early in the second round.

Diaz doesn't concede that he would have lost had the injury not occurred.

"I think it would have went better for me in the later rounds anyway," Diaz said. "It was already starting to turn around early in the second round."

He gets a chance to show that he deserved the title when he takes on Junior Assuncao tonight at the Palms.

This bout should offer a better matchup for Diaz than did Gamburyan, who prefers to keep fights on the ground.

"(Assuncao) is tough and he's ready to fight," Diaz said.

The card, which features many competitors from past seasons of the show, is the lead-in to the debut of the sixth season tonight on Spike.

First season runner-up Kenny Florian will take on fourth-season semifinalist Din Thomas in the main event. The winner will move closer to the top of the lightweight division, where the title situation is cloudy because of champion Sean Sherk's upcoming appeal hearing of a positive steroid test.

Florian has already had his chance, losing to Sherk in October. Thomas, a nine-year veteran who only now is starting to achieve stardom, is awaiting his opportunity.

"I don't know about Kenny, but I think if I win, I deserve a chance," Thomas said. "He had his chance. But I guess if I feel I deserve it and he beats me, then I guess he would deserve it then, too."

Two fighters who know they will compete for a title are Matt Hughes and Matt Serra. The two will coach the respective teams on this season of the reality show.

At the end of the season, Serra will defend his welterweight title against ex-champ Hughes.

The first episode sets the stage for a contentious relationship between the two, which is likely to continue throughout the season and all the way up to their fight.

Also at the Palms tonight, Nate Quarry returns from a serious back operation after nearly two years away from the UFC to take on Pete Sell.

A middleweight bout between Chris Leben and Terry Martin is also featured on the card, which begins at 3:45 p.m., with the televised portion beginning at 6. The telecast will be shown tape delayed at 9 on Spike (Cable 29). The debut episode of Season 6 of "The Ultimate Fighter" follows at 11.