Eddie Hearn, Anthony Joshua’s promoter, is scared of the potential fight against Deontay Wilder.
"As much confidence as I have in Anthony Joshua, I know the dangers of that fight. It's the same as I felt in the Klitschko fight, but the difference in this fight is it's two guys in their prime," he said.
There’s no doubt, Anthony Joshua is a world class fighter.
He’s only 28, and is a world champion after taking up the sport aged just 18.
His astronomical rise has not been easy, however. He was rocked by Wladimir Klitschko, and eventually knocked down on his last legs for much of the fight.
His recovery was the true test of a champion, but there was the underlying worry that he may have taken on too much, too soon.
Eddie Hearn implied that Joshua took the fight against Klitchscko “against advice”, and is worried he will do the same against Wilder.
"Anthony likes to jump in and take fights, sometimes against advice like against Wladimir Klitschko.
"Two young, fast, athletic punchers and that's why it's the biggest fight in world boxing."
Hearn has been doing his best to delay the fight, despite pressure from Wilder who has recently ‘declared war’ on Anthony Joshua.
The general feeling is that there are a couple of candidates Joshua could fight next, including the mandatory defence of his title, a bout with New Zealander Joseph Parker, or perhaps a showdown with Tyson Fury.
Such fights would give him time before facing a genuine threat, a rising star as good as himself.
Ultimately, however, Hearn gave Wilder fighting words to think about.
"Deontay Wilder has been doing a lot of talking, but unfortunately he's called the bluff of someone who loves a fight and loves to compete, and someone who loves to fight as well.
"This fight has just started to explode and it's going to get bigger and bigger.
"We have a responsibility to fight fans to make sure the best fights are made and this is the best fight in world boxing."
One thing is for sure: when Wilder and Joshua do meet, it’s going to be the fight of the decade.