Exhaustion and a virus disrupted Anthony Joshua's training camp ahead of his victory over Dominic Breazeale, Eddie Hearn has revealed.
The Londoner (17-0-KO17) made the maiden defence of his IBF world heavyweight title with a seventh-round stoppage of Breazeale at The O2 on Saturday night - but did so having struggled for rhythm in his preparations.
Hearn told Sky Sports: "Behind the scenes, and he wouldn't talk about this kind of thing because it seems like he's making excuses, but he didn't have a great camp.
"He had a situation where he boxed Charles Martin and had two weeks' rest, but that rest involved commercial appearances, broadcast appearances and sponsorship obligations. By the time he went into the camp, he was still tired.
"Three weeks ago, he came down with a virus and there were a couple of doubts about the fight at one stage. He went in the ring in great condition, but Breazeale was tough and there have been fighters that have wilted.
"I spoke to him and he realises he has to pace himself. As we step up in level, it is going to be harder and harder to get these guys out of there. When he got rid of Breazeale, he thought, 'Thank God for that'.
"On Saturday, he exerted enough energy, he busted his nose and crashed out a few shots. Breazeale was the perfect test for the first defence.
"In nine months, Anthony Joshua has boxed four undefeated opponents, he has won the Commonwealth, British and the world title heavyweight title and defended it. It is not just the fight - people will say Gary Cornish was one round - it's the camp. It is eight to 10 weeks of solid training for every one of those fights.
"Now, he's going to go off and I said to him to be a young man, have a laugh, go to the beach, hopefully where nobody knows you, which I know is difficult these days.
"When we left that weigh-in on Friday, he was bundled in the Range Rover and people chased him down the street. It's great to see in boxing, but that drains you in itself. The adulation is fantastic, but it takes it out of you, too. Young kids look up to Anthony Joshua and we should embrace him."
Joshua will now take a lengthier break before his next defence, which could be against the likes of mandatory challenger Joseph Parker, WBC world champion Deontay Wilder or domestic rival David Haye.