Martin Murray: Kell Brook won't last more than six rounds vs. Gennady Golovkin

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Martin Murray does not expect fellow Briton Kell Brook to last beyond six rounds with Gennady Golovkin.

Brook steps up two weight divisions to challenge Golovkin for the WBC, WBA and IBF world middleweight titles at the O2 Arena in London on September 10.

Golovkin (35-0, 32 KOs), 34, has stopped his last 22 opponents and none of his world title fights since 2010 have gone the distance.

Murray (33-4-1, 16 KOs) became the opponent to last the longest with the US-based Kazakhstan boxer when he went 11 rounds against the world's No 1 middleweight in Monte Carlo in February 2015.

But Murray, 33, believes the size difference will be too much for IBF world welterweight champion Brook (36-0, 25 KOs).

"It's a step too far for Kell," Muray told ESPN. "Golovkin is another level and he's in deep, deep water and I don't think he's going to be able to swim.

"I don't think Kell can go as long as I did with him. I think it goes five rounds, six maximum, and I know what it is like in there with him. It could go early.

"I've gone the longest with Golovkin and to beat him you have to move well, which Kell does, and you have to push him back. That's how you beat him but I don't think anyone is strong enough at middleweight to do that.

"Kell has got great range, distance and timing so Golovkin is going to be in with something different himself. But Golovkin's distance and timing are something else. He's in a different league to anything I've fought and Canelo [Saul Alvarez] won't touch him.

"Golovkin really hurt me with the body shots he took me down with. I gritted my teeth and got back up but when those body shots hit you, you don't recover. It was the same with [fellow Briton] Matt Macklin [who Golovkin knocked out in three rounds in 2013]. It was the little shots he hit me with as well, the range finding shots, and he's just on a different level.

"Kell has been in some hard fights like when he fought Carson Jones and he's improved since then. He showed grit to win that fight against Jones because at one point it didn't look like he would. But Golovkin has not once looked like he would get beat.

"Fair play to Kell for taking it because this is not his natural weight. He's obviously getting well paid for it and he gets to keep his welterweight title and he was struggling to get the fights he wanted at welterweight."

Murray, who declined the chance to spar with Brook as he had not yet resumed training, is considering a return to middleweight.

The St Helens boxer stepped up to super-middleweight where he was beaten on points by Arthur Abraham for the WBO world title in November and then out-pointed by fellow Briton George Groves in June.

Murray has fought for the world middleweight title three times -- drawing with Felix Sturm [2011], losing on points to Sergio Martinez [2013] and stopped by Golovkin last year.

"I'm looking at a November return and I'm not 100 percent decided, but maybe at middleweight," Murray told ESPN.

"I moved up because it was killing me making the weight. I thought I should've got the decision against Abraham but I wasn't right for the Groves fight. Both of them had a massive size advantage against me.

"Down at middleweight will be harder to make the weight but I feel I've got the advantage there."