Kell Brook could step back down to welterweight to face Errol Spence but might not "reach the same performance levels", says promoter Eddie Hearn.

The 'Special One' is still the reigning IBF world champion at 147lbs despite moving up two divisions to unsuccessfully challenge middleweight king Gennady Golovkin in September.

The governing body has informed Brook (36-1-KO25) and his team that if he wants to remain champion negotiations to face mandatory challenger Spence (21-0-KO18) must begin on October 26.

Brook said in the build-up to the Golovkin fight that he no longer considered himself a welterweight and while Hearn is concerned about his fighter stepping back down, he is not ruling out taking on the American known as 'The Truth'.

"At the moment we are keeping all our options open," he told Sky Sports.

Errol Spence Jr is Kell Brook's mandatory challenger at 147lbs

"Kell can make 147 but I don't think he can necessarily reach the same performance levels. The Spence fight is a big fight for us, especially at 75/25 so it's definitely something to take seriously."

Brook is still recovering from surgery following a broken eye socket sustained against Golovkin but trainer Dominic Ingle says the Sheffield star will be back in the ring "sooner rather than later" and wants a big-name on his return.

"The GGG fight has given Kell a number of high profile options but I think realistically his next opponent comes from Spence, Canelo, Cotto or Khan," said Hearn.

Kell can make 147 but I don't think he can necessarily reach the same performance levels. The Spence fight is a big fight for us, especially at 75/25 so it's definitely something to take seriously. Eddie Hearn

IBF chairman Lindsey Tucker concedes Brook's injury could yet delay a showdown with Spence but is sticking to the October 26 deadline, whatever the outcome.

"A couple of things could happen," Tucker told The Ring Magazine. "He could say he's giving up the title to move up in weight.

Brook says he could have gone blind if his corner had not thrown in the towel against Gennady Golovkin Brook says he could have gone blind if his corner had not thrown in the towel against Gennady Golovkin

"He could come up and say that he suffered from an eye injury and he needs some additional time, so we could give him a medical extension.

"But we won't know unless they come to us and say 'we're giving up the title' - we won't know anything before then."

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