Frank Warren insists Alexander Usyk will not quit heavyweight in search of more glory at flyweight.

Usyk was previously the undisputed lightweight champion, becoming undisputed at heavyweight when he defeated Tyson Fury last May and remains undefeated after winning a rematch with Fury last month.

The Ukrainian has previously stated that he may then return to lightweight.

But Frank Warren, who promotes IBF heavyweight champion Daniel Dubois, isn’t convinced.

“He wouldn’t. Look at his size, it’s impossible,” Warren told sky sports.

Usyk has not fought at lightweight since 2018 and is now firmly established at heavyweight. In his last five games, he has consistently weighed over 220 pounds.

“You just look at his size, it’s not going to happen,” said Warren, who expects Usyk to defeat the winner of Dubois’ Feb. 22 IBF title fight with Joseph Parker.

Noting that this was the most lucrative fight, Warren said, “To him, it’s the winner of this fight. A big fight, a massive fight.”

Warren is backing Britain’s Dubois to beat his next challenger, in-form New Zealand’s Parker.

“I’m going to be confident after the fight. I trust him, that’s why we’re in the fight, but anything can happen with these big guys. They’re big guys. They throw bombs, both of them,” the promoter said.

“Parker doesn’t look like a newbie. He’s been there, done that, became a world champion. He’s in great shape now. You see, he had a fighter’s heart in the fight with Zhang Zhilei. He fell to the floor twice. I still gritted my teeth and survived that battle.”

Dubois boxed with Usyk in 2023, when Usyk was stopped in nine rounds. Usyk himself did visit the canvas during that fight, but suffered a low blow. He took the allotted time to regain his strength, then rose to hold off the Englishman.

But despite this, Warren still believes in Dubois’ ability to defeat the co-champion.

“I really still believe he would have beaten Usyk if it wasn’t for what was going on in his head with the referee at the time,” the promoter said. “That four-minute break. He would jump on him.

“Is it a low blow? I don’t think it’s a low blow, some people think it is. But the most important thing is four minutes, when he (Usyk) wanted to fight himself, the referee said more time is needed ”

Now, however, Dubois has blossomed into a dangerous world champion after defeating Anthony Joshua in just five rounds in September.

“Ninety percent is mental,” Warren said. “It’s going to take time. He’s had some hiccups along the way, but you look at the battles he’s been through and the things he’s done – he’s learned his lessons.

“He’s a very young lad. He’s mentally mature, which is very important. He’s got skills. He’s very comfortable with (coach) Don Charles, he’s done a great job with him and now it’s his time. “

Warren believes that by the end of the year, Dubois, not Usyk, will be the undisputed heavyweight champion of the world.

“If he can get through it and fight Usyk…” Warren said, “…I do think (he will).”