AJ, 36, is due to face The Problem Child, 28, on December 19 in Miami in what will be his first fight since his September 2024 clash with Daniel Dubois, and his promoter has now insisted the former heavyweight champion is ready for Paul.
Speaking to talkSPORT, Hearn said: “He's good, he's really dialled in as if he was fighting an elite heavyweight.
“The one thing he always does is take everything seriously and he is doing so for this, he's in tremendous shape.”
Joshua, who has never previously faced a contracted weight cap in his professional career, has already hit 244.7lbs with two weeks to spare, posting an image of himself on the scales shortly after Hearn’s update.
Hearn said the strict limit of 245lbs has made Joshua "a lot lighter" than he usually would be for a fight.
The Matchroom Boxing promoter said: “The difference in this fight is he has to make a specific weight which is a lot lighter than he would be going into this fight.
“But he’s on track and is in Miami with not long to go until the fight. I can’t believe what’s about to happen to be honest.
“Yeah he's ready to go and do a job on him, and I just can't believe we've signed the contract to fight him.”
The bout has attracted widespread backlash from traditional boxing fans, with many questioning why a former unified heavyweight champion is facing a YouTuber-turned-boxer.
However, the fight will count on Joshua’s professional record and has been fully sanctioned by the Florida Athletic Commission.
Hearn dismissed any suggestion of staged elements.
He said: “I mean it's not going to be an easy night work for Jake.
“People keep coming up to me and asking if there is a script. First of all of course there isn’t. Then I said ‘actually yeah, there is a script — we are going to go out in the first round and smash him to bits.’”
Joshua has undergone a major shift in training setup for this fight.
After elbow surgery earlier this year, he relocated to Spain and linked up with Oleksandr Usyk’s, 38, team - a surprising move given their rivalry.
While he is not sparring The Cat, AJ is embedding himself fully into the camp environment as he seeks new motivation and structure following his stint with trainer Ben Davison.
