Even if MMA and boxing experts are giving him little or no chance to pull off the upset, Conor McGregor is confident that he will beat Floyd Mayweather on Aug. 26. The UFC lightweight champion fully expects to hand the undefeated boxer the first loss of his professional career.

McGregor would have to do so in his first-ever boxing match since he’s only fought in MMA as a pro. But the betting underdog isn’t only convinced that he’ll win—he believes that he can knock Mayweather out in short order.

READ: Floyd Mayweather vs. Conor McGregor Betting Odds

“Last night I landed at LAX and Conor landed at the same time from Ireland. We both landed at the same time and I was waiting for him to get out of the plane. He gets off a flight from Ireland, looks like he was just fitted at Armani, walks off the plane and says, ‘I will knock this man out within four rounds,”’ UFC president Dana White said Monday on FS1’s “Speak For Yourself.”

Scoring an early knockout would be nothing new for McGregor. It’s how he’s dominated UFC, beating the likes of Eddie Alvarez, Jose Aldo and Chad Mendes within the first few rounds.

Repeating that same kind of success in boxing against the sport’s best athlete of the last two decades seems to be nearly impossible. White, however, says he’s learned to no longer doubt McGregor.

Prior to his UFC featherweight championship fight at UFC 194 in December 2015, the bout that truly elevated him to superstardom, McGregor had been boasting that he would knock out Aldo in the first round. Facing the greatest fighter in the history of the 145-pound division, McGregor needed just one punch and 13 seconds to win the belt.

“Conor is a madman. Conor is a madman. He’s gonna let Floyd know what he’s gonna do and how he’s gonna do it and everybody’s been saying to me this whole time, “‘Do you think that Conor can really beat Floyd Mayweather?’ Pacquiao just got beat by a school teacher.”

White, of course, is referring to Manny Pacquiao’s recent loss to the relatively unknown Jeff Horn. The general consensus seems to be that the judges wrongly handed Horn a unanimous decision victory, though Pacquiao was far from dominant and the fight was much closer than it was expected to be.

Mayweather has had few close calls in his career, even when facing elite competition.

His only ever split decision victory came against Oscar De La Hoya in 2007, though it was clear he won the fight. One judge inexplicably scored his 2013 fight against Canelo Alvarez as a draw, but Mayweather was dominant and won by majority decision.

READ: What Floyd Mayweather's Father Thinks About Him Fighting Conor McGregor

Marcos Maidana gave Mayweather one of the biggest challenges of his career when they met on May 3, 2014. Mayweather was awarded a majority decision, and he cruised to a unanimous decision win in their rematch four months later.

There is a large contingent of the public that believes McGregor can actually beat Mayweather. Most of the wagers at Las Vegas sportsbooks are for McGregor to win, and the UFC star has much better odds to win by knockout than a 12-round decision.