Chael Sonnen vs. Wanderlei Silva Official for Sao Paulo Venue on May 31

As rumors began to swirl that a long-awaited grudge match between Chael Sonnen and Wanderlei Silva would not actually happen, UFC officials confirmed last night that the bout is now official for a "Fight Night" event on May 31. 

As MMA Fighting first reported at the conclusion of UFC Fight Night 38 last night, "The American Gangster" and the top Brazilian foe in his crosshairs, Silva, will clash at the Ibirapuera Arena in Sao Paulo, Brazil. 

The two rivals are currently head coaching opposite one another on Season 3 of The Ultimate Fighter: Brazil and were briefly expected to butt heads at UFC 173, which takes place during Memorial Day weekend, per MMA Junkie. 

However, that bout was quickly moved to a "Fight Night" card on May 31 that is yet to be formally named, per MMA Mania, though it will more than likely be the TUF Brazil 3 finale. 

Since then, the matchup has become somewhat of a question mark, especially after UFC president Dana White confirmed that "The Axe Murderer" was yet to sign the fight contract, per Fox Sports.

In the past week, Sonnen has had no issue airing his displeasure with Silva refusing to make their bout official.

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Why won't he sign? What else is he going to do? Go play tennis? That's out. He's got a racket but has no balls.

— chael sonnen (@sonnench) March 17, 2014

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Hey doofus, paper. Pen. Sign. If they put your brain in a bird, it would fly upside down.9 days to sign or I release those.. Well, you know.

— chael sonnen (@sonnench) March 22, 2014

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This tweet was posted early yesterday morning, prior to the UFC formally announcing Sonnen vs. Silva. 

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8 days left. Still no signature.

— chael sonnen (@sonnench) March 23, 2014

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While Sonnen has lost three of his past four contests, all were against household names in Anderson Silva, Jon Jones, Mauricio Rua and Rashad Evans. 

His sole victory came against "Shogun," whom he defeated at UFC Fight Night 26 in August via a guillotine choke in the first round. 

Meanwhile, Silva has alternated wins and losses for the promotion since February 2010, posting a 3-2 record during that time frame. 

Most recently, Silva delivered a vintage knockout over Brian Stann at UFC on Fuel 8 a little over a year ago. 

With this fight now finally looking like a sure thing, who will put the exclamation point on this feud and walk away with lifelong bragging rights?

John Heinis is a featured columnist for Bleacher Report. He is also the MMA editor for eDraft.com.