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For the second time, Conor McGregor appeared to retire from mixed martial arts.

With little warning, the former UFC featherweight and lightweight champion tweeted early Tuesday morning he had "decided to retire from the sport formally known as 'Mixed Martial Art' today."

ESPN.com's Brett Okamoto shared a statement from UFC President Dana White, who seemed to confirm McGregor is "retiring from fighting."

McGregor last fought at UFC 229 in October, losing to Khabib Nurmagomedov via submission. The two brawled after the fight, leading to suspensions for both fighters. McGregor received a six-month ban that went into effect the night of the event, so he'd be eligible to return to the Octagon on April 6.

This isn't the first time the 30-year-old used Twitter to proclaimed his career was over. In April 2016, he wrote he had "decided to retire young."

The timing of McGregor's cryptic announcement was even more puzzling because he was a guest on The Tonight Show on Monday. McGregor told host Jimmy Fallon he was in talks with the UFC for a return in July. However, he added he's "set for life" and that he "[doesn't] necessarily need to fight."

When McGregor "retired" in 2016, it was part of a protracted battle with the UFC after the promotion pulled him from UFC 200. The company was unhappy with him for failing to take part in promotional events leading up to the pay-per-view.

The two sides worked out their differences and McGregor defeated Nate Diaz at UFC 202 in August 2016, avenging his defeat to Diaz at UFC 196 earlier in the year.

Should McGregor be unhappy with the state of negotiations with the UFC over his next fight, Tuesday's tweet could be a way for him to exert some leverage. As arguably the company's biggest star, he's in a position to basically name the time and place and handpick his next opponent.

Of course, nobody should put it past McGregor to abruptly walk away from MMA altogether. As he said to Fallon, he has already made more than enough money to retire now and live comfortably for the rest of his life.

ESPN.com's Dan Rafael reported McGregor was guaranteed at least $30 million from his boxing match with Floyd Mayweather in August 2017. Rafael noted McGregor's total earnings would likely top $100 million when factoring in the pay-per-view buys, ticket sales and other revenue sources.