Conor McGregor is looking to do the impossible taking on Floyd Mayweather in his first-ever professional boxing match. While the UFC’s biggest star has never competed inside the squared circle, he’s had plenty of fights inside the octagon.

What is Conor McGregor’s record? That’s a question that can be answered in a few different ways.  

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Since signing with the UFC, McGregor has just one loss on his resume. He’s got a 9-1 record with the world’s No.1 MMA promotion, having suffered his only defeat at the hands of Nate Diaz at UFC 196 on March 5, 2016.

McGregor proved to be beatable, though it came under unusual circumstances. Entering the fight with Diaz with a 7-0 record, the Irish Fighter had only competed in UFC’s 145-pound featherweight division. He was supposed to make the leap to the 155-pound division and take on lightweight champion Rafael dos Anjos, but the champ was pulled off the card with an injury. Replacing dos Anjos on just 11 days notice, Diaz asked that the bout would be fought at 170 pounds.

Jumping up two weight classes, McGregor tapped out to Diaz in the second round of their fight. But he got his revenge in the main event of UFC 202 five months later, beating Diaz by unanimous decision at 170 pounds. McGregor went on to win the lightweight title from Eddie Alvarez with a second-round knockout less than three months later, and he’s picked up wins against all nine fighters he’s faced in the UFC.

None of those victories were cheap ones. Even before deciding to fight the best boxer of his generation, McGregor was always willing to take on a challenge. He defeated Jose Aldo, the best featherweight of all time, in just 13 seconds. McGregor’s resume also includes a unanimous decision victory over current 145-pound champion Max Holloway. The two fighters met in 2013, and Holloway has since won his last 11 fights.

McGregor’s other UFC wins have come against Marcus Brimage, Diego Brandao, Dustin Poirier and Dennis Siver. He also defeated Chad Mendes with a second-round knockout at UFC 189. Mendes replaced Aldo, who couldn’t fight because of an injury.

Prior to heading to the UFC, McGregor had 14 professional MMA fights. Competing with Cage Warriors, an MMA promotion based in London, McGregor went 12-2. He had his first fight with the promotion in 2008 when he was just 19 years old.

That gives McGregor a total career record of 21-3.

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McGregor seemingly has no chance to defeat Mayweather, who has mastered the sport of boxing for two decades, but the UFC star’s knockout power has convinced some of the public that he can pull off the upset. Seven of his nine UFC wins have come via knockout, and McGregor knocked out 11 of his 14 opponents before going to the UFC.

McGregor has never been knocked out in his career, and all three of his losses have come via submission. That almost certainly won’t be the case in his boxing career when he goes up against Mayweather on Aug. 26.