Conor McGregor further cemented himself as the biggest name in MMA when he defeated Eddie Alvarez at UFC 205 on Saturday, and now the new lightweight champion is coming after the biggest draw in all of combat sports. After rumors circulated earlier this year that Floyd Mayweather could potentially take on McGregor in a boxing match, the UFC star is challenging the undefeated fighter.

Mayweather has claimed to be retired from boxing since he defeated Andre Berto in September of last year, but McGregor is hoping to get the former champion back in the ring. McGregor has said he’s willing to step into Mayweather’s world and face him in a boxing match for a nine-figure payday.

“As far as real fighting, true, pure unarmed combat, Floyd don’t want none of this,” McGregor told TMZ. “Give Floyd a shout; tell him I’m coming. Tell him to run around Showtime offices. I want $100 million to fight him under boxing rules because he’s afraid of a real fight.”

McGregor’s challenge has forced many in the sports world to ask the same question: could McGregor actually beat Mayweather in a boxing match?

The fight is likely a pipe dream that will never be realized, but that hasn’t stopped analysts from treating it like a real possibility. It’s a topic that’s been discussed heavily on ESPN and other media outlets, and the fight would likely generate millions of pay-per-view buys.

Some have argued on behalf of McGregor, claiming that he could at least give Mayweather a challenge because of his striking ability. While many MMA fighters are strongest on the ground, it’s McGregor’s left hand that is his most dangerous weapon. He won the 155-pound UFC title on Saturday by utilizing his superior boxing skills, knocking out Alvarez with a combination of punches that forced the ref to stop the fight.

However, most agree that McGregor would have no shot against Mayweather in a boxing match. McGregor’s striking skills are no match for most MMA fighters, but he likely wouldn’t be able to land any blows of significance against one of the greatest defensive boxers of all time.

Mayweather has only been knocked down once in his 49-fight career. Having made a living off of dodging punches against some of the best boxers of his generation, he would have no problem doing the same against a fighter that would be making the transition to an entirely new sport.

Las Vegas oddsmakers agree that McGregor would be an extreme longshot. Jeff Sherman, who manages the Westgate SuperBook in Las Vegas, says McGregor would be a +1100 underdog in such a fight. Mayweather would have -2500 odds, meaning gamblers would have to risk $2,500 in order to win $100.

To put those numbers into perspective, Mayweather is a -265 favorite in a potential rematch with Manny Pacquiao, whom he defeated by unanimous decision on May 2, 2015. When Buster Douglas defeated Mike Tyson in 1990 in one of the biggest upsets in boxing history, he was a +4200 underdog.

As a heavy underdog, McGregor would be in an unfamiliar position. He was a -165 favorite before his fight with Alvarez, and he was the betting favorite in both of his fights against Nate Diaz in 2016.

McGregor is 9-1 in his UFC career, having suffered his first loss at UFC 196 in March. He is the only fighter in UFC history to hold titles in two different weight classes at the same time.