The best boxer in the world against the best mixed martial artist in the world inside a boxing ring? The mere thought of such a possibility makes all kinds of ideas run through a fight fan's brain.

But the person who'd have to sign off on such thing for the UFC welterweight champion to crossover into another combat sport isn't as keen on the idea. During an interview to promote Saturday's UFC Fight Night event in London, UFC President Dana White dashed the hopes of Canelo vs. Usman from taking place. 

"I've already said before, I will stop Canelo," Usman said. "At the end of the day, it is what it is. Everyone's like, 'Oh man, he's the best boxer in the world. You can't do it. No one can do it. That's fine because I've said before, it can't be done until it's done."

White didn't say whether he's talked to Usman about his desire to face Alvarez. However, even if Usman can somehow convince him that he can beat Alvarez and should attempt to make the fight, White isn't too sure if there is an appeal from boxing and MMA fans to see a matchup between the premiere combatants in their respective sports.

“I don’t even know how many people would be interested in seeing that,” White said. “It’s like when Conor [McGregor] and Floyd [Mayweather] fought [in August 2017]. It sort of took on a life of its own. They talk about Tyson Fury and Francis [Ngannou], too. What do you think’s going to happen in those fights? Those guys are the best in the world at boxing.

“It’s a fight that took on a life of its own. Everywhere I went, people asked me if those two are going to fight, and it just kept building and building and building. Finally, it got to the point where I was like, this is big, and I was right. It ended up being the biggest pay-per-view ever.”

Alvarez (57-1-2, 39 KOs), the reigning undisputed super-middleweight champion, returns to the ring on May 7 when he moves up a weight class to face WBA (super) light heavyweight champion Dmitry Bivol on DAZN PPV in the United States and Canada (check your region for availability on DAZN). 

Meanwhile, Usman (20-1) is coming a unanimous decision win over Colby Covington at UFC 268 to successfully defend his welterweight title for the fifth time.