Chael Sonnen vs. Nick Diaz? Sonnen says it nearly happened at UR Fight...

Chael Sonnen returns to the mats this Sunday when he welcomes old foe Michael Bisping in an exhibition grappling match at UR Fight, the curious one-off event set to showcase a mish-mash of combat sports at Phoenix's Celebrity Theatre. And while four years may have passed since Sonnen and Bisping first threw down on FOX, the retired UFC contender is confident history will repeat itself come March 20.

"Oh, he has no chance," Sonnen told MMA Fighting. "He has absolutely no chance. I will lay on top of him for 15 minutes and then go home. I might submit him. I'm certainly going to try, but he's not going to go anywhere. I'm going to take him down and whisper in his ear: ‘welcome to the next 15 minutes of your life.'"

Sonnen and Bisping's unofficial rematch is part of a triple-header which also features a pro wrestling match between Kurt Angle and Rey Mysterio, as well as a boxing attraction which sees one of the sport's greatest champions, Roy Jones Jr., fight a contest-winning fan. MMA legends Dan Severn and Tank Abbott were also slated to take part in a rematch of their 1995 marathon bout, however Abbott was forced out after failing a pre-fight physical.

If it all sounds bizarre... well, that's because it pretty much is.

The event is the brainchild of URShow.tv, an online content network which also produces Sonnen's new political show, The Republic of Sonnen. And according to Sonnen, the initial UR Fight pitch was even farther out of left field than the oddball card the team settled on.

"They were talking about wanting to do something like this, and the first time I talked to them, they said, ‘what do you think about boxing Roy Jones Jr.?'" Sonnen said. "They were going to do it on a rooftop in Abu Dhabi, and I said, ‘well, I'll whip Roy's ass right now, but I'm on suspension. I can't fight anywhere if I wanted to. If you want to wait two years, then I can do it.'"

Instead Sonnen was tasked with a commentary role to call Jones Jr.'s fight, though in true "American Gangster" fashion, he ended up being part of the show himself.

Sonnen at first enlisted former UFC champion Quinton "Rampage" Jackson as an opponent for the grappling portion of the card. Jackson, like Sonnen, has a new program airing on URShow.tv -- Rampage is Human -- however complications with Jackson's employers at Viacom ultimately forced Sonnen to look elsewhere.

Luckily, with a sizable purse at stake, no shortage of surprise names jumped at the opportunity.

"I was kind of tasked with it. I was their connection to MMA," Sonnen said. "So the first guy I called was Randy Couture, and he accepted instantly. Then, while we were still on the phone, he went and looked at his calendar and was like, ‘hey, I can't even be in the state, I have (to film) a movie in a whole other state, I can't be in Arizona.' So he was out. I went to Forrest (Griffin). Forrest liked the idea, but he's an executive at Zuffa right now, or whatever he is, and he didn't think he could go anywhere else.

"I went to Rashad (Evans); Rashad had a fight with Shogun (Rua) lined up. I went to Nick Diaz. Nick loved it. Nick was in. But then I didn't hear back from him. We didn't hear in time, and I was kind of telling him, hey, this is a rushed deal. I was getting ready to leave town myself to go film Celebrity Apprentice and I had to have it done in like 30 minutes. That didn't work out. So I called Bisping and he accepted instantly, and that was it."

Sonnen and Bisping infamously met in 2012 at UFC on FOX 2, where Sonnen edged out a tight unanimous decision to earn a shot at the UFC middleweight belt.

This time, the two are expected to compete in an openweight contest for three five-minute rounds under Metamoris rules, meaning a submission is the only path to victory. With Bisping mere weeks removed from an electric UFC win over Anderson Silva, Sonnen expects to arrive on Sunday with a weight advantage that borders on 20 pounds.

The two former rivals are good friends these days, although Sonnen wouldn't be surprised to see much of the same chippiness reemerge from their first fight, which Bisping still adamantly believes he won.

"I think there's some of that," Sonnen said. "I was pretty objective about that night. I didn't know who won that fight. And he was always resentful of the testosterone rules, the testosterone era that was going on, and I'm not sure he didn't have a fair complaint there. I'm not sure that he's wrong on that. The rules are what the rules were, so yeah, I think there's a little bit (of animosity left).

"But I'm coming at it from more of a respect standpoint after being in there with him. I respect his skills a lot. I respect his heart and how hard he goes, all of that stuff. So I've always appreciated Bisping. I appreciated him more after I competed with him, but that's where it ends. I'm going to go at him as hard as I possibly can."

With both Sonnen, 38, and Bisping, 37, hovering around their late thirties, Sonnen admits he thinks about returning to the fight game often.

His drug suspension comes to an end in July, potentially paving the way for a comeback his manager Mike Roberts insists may very well happen for "the right fight."

A third crack at the 40-year-old Silva would appear to be exactly the kind of fight Roberts is talking about. But at least for now, Sonnen has a hard time seeing himself return to make one last walk.

"I'm done. I'm retired," Sonnen said. "I wish him (Silva) the best, and when he fights, I tune in. I feel attached to his career, at least on some levels, and I like to see him do well. I love that he's still out there competing and I cheer for him when he fights.

"But if you're asking if I'm going to come back to kick Anderson's ass a third time, I'm not coming back to kick any of their butts. But if you're asking me if I could... of course I could. Come on. You're talking to the greatest middleweight to ever live. Of course I could. I kicked everyone's ass in that division so handily that I left the division, and left it on my own looking for a challenge. Come on. You've got to be serious now."