Joshua, a former two-time heavyweight champion, was dropped a staggering four times by Dubois before suffering a fifth-round KO at Wembley in September.
Following the defeat, the Watford-born boxer was on course for a do-or-die rematch with Dubois on February 22, but while revealing the extent of the 35-year-old’s injury, Hearn said the proposed date came too early for Joshua.
He said, “We had a very awkward call,” he told Boxing News.
“He wanted to fight on February 22 and basically was told that there is no way you can start camp and be 100 per cent for February 22 physically.
“There’s nothing major.
“There are two or three issues that he had a little bit in camp and after the fight.
“So when he comes back in May or June or whenever that’s going to be, you have to be physically mentally 100 per cent ready.
“He wants to rematch Daniel so bad.”
Meanwhile, Hearn added that Joshua didn’t suffer a major injury.
“There’s no major injury,” he added.
“Every fighter has niggles in camp, especially when you’re a heavyweight who trains every day and spars really hard.
“There’s nothing that’s going to be a long-term problem.
“For a turnaround after a five- or six-week break after a defeat like that, it’s just not possible to be a hundred per cent.
“There’s no tear in the bicep, just wear-and-tear that means he cannot go into a training camp with the same intensity that he would want to.”
Meanwhile, a fight between Joshua and Tyson Fury, who has long been linked with a super fight with the Watford-born boxer, is being considered.
First, Fury will face unified champion Oleksandr Usyk on December 21 after losing to the Ukrainian in May.
