Veteran trainer Dave Coldwell has a realistic fear that IBF welterweight champion Kell Brook could end up like Roy Jones Jr. on Saturday night.
In 2013, Jones was the undisputed light heavyweight champion and made a decision to move up by 25-pounds to the heavyweight division. The dangerous gamble paid off, as he pulled off a historic feat by capturing the WBA world title from John Ruiz.
But in his next fight, Jones cut the added weight and returned to the light heavyweight division. He was never the same again. The man who was once considered to be unbeatable, struggled to get a close decision over Antonio Tarver, and then went on a three fight losing streak - including two knockout defeats.
A similar scenario takes place this coming Saturday night.
Last September, Brook made a 13-pound leap by moving up by two weight divisions to challenge IBF, IBO, WBA, WBC middleweight champion Gennady Golovkin at the O2 Arena in London. Brook was stopped in five rounds.
This weekend, he drops back to the welterweight division to make a mandatory defense against undefeated Errol Spence at Bramall Lane in Sheffield.
"I think the weight is a massive issue in this fight. If you go through and look at the past I remember, this could be quite similar and crucial, when Roy Jones Jr moved up to heavyweight," Coldwell told Sky Sports.
"He (Jones Jr) put on muscle and was in shape when he fought John Ruiz. We all thought he was fantastic, but when he came back down to light-heavyweight he was never the same. His durability had gone, his reactions were a fraction slower and we all know what happened to his career after that.
"That is my worry for Kell Brook in this fight because when he boxed GGG, he was ripped up and we were all talking about how much of a machine he looked like at middleweight. Now he has to strip that muscle."