Frank Warren remains flabbergasted by Joe Joyce’s decision to slim down for his first fight with Zhilei Zhang. 

Joyce, the  heavyweight bruiser from London, weighed 256 pounds ahead of his showdown with China’s Zhang in April, about 15 pounds lighter than his previous fight against Joseph Parker last September, in which he weighed 241 ½ pounds. Joyce knocked out Parker in the 11th round.

But after what many regarded as a career-best performance, Joyce ended up getting stopped in his next fight by the southpaw Zhang, who weighed 278 pounds for that contest, in the sixth round at Copper Box Arena in London.

Their rematch will be held this Saturday at London’s Wembley Arena in a fight that will determine an interim champion for the WBO heavyweight title, which is currently held by Ukraine's Oleksandr Usyk.

Warren, Joyce’s longtime promoter, said he believes his charge is better off fighting at a heavier weight. Joyce has only weighed above 270 pounds twice in his career; he started his career fighting around 250 pounds, before settling into the 260 range.

“I was quite shocked when they announced the weights [leading into the first fight],” Warren said on talkSPORT radio. “Maybe they thought he was going to be more mobile. It didn’t work out. [Against] Joseph Parker, I thought that was a phenomenal performance. It was a good fight. Parker is one of the top heavyweights in the world and he done a job on him.

“So, I’m hoping this time around that he comes in around that weight again. That is his optimum weight, that’s the weight he boxes the best at. And hopefully we get the result on Saturday.”

Warren pointed out that Joyce (15-1, 14 KOs) is at a crucial stage in his career; another loss to Zhang (25-1-1, 20 KOs) will cause the 38-year-old to lose his perch atop the heavyweight rankings.

“Joe knows he can’t afford to slip up on this,” Warren said. “At this age—and Zhang’s age—they’ve got to keep that seat, as I always say, at the top table. Eventually, the mandatory is going to be called for the respective champions. As far as the WBO is concerned, the winner of this fight will be the interim champion and the WBO champion will have to defend against him sometime next year.”

Sean Nam is the author of Murder on Federal Street: Tyrone Everett, the Black Mafia, and the Last Golden Age of Philadelphia Boxing.