Eddie Hearn has admitted he was stunned by Anthony Joshua's punching prior to his win over Otto Wallin in December.
And the boxing promoter is expecting AJ to put Francis Ngannou to the sword when they fight in Saudi Arabia next month.
Joshua is currently training for the bout in the Middle East, which is set to be watched by millions around the world on March 8.
Some wrote the Briton off as a faded force after his two defeats to Oleksandr Usyk in 2021 and 2022 respectively.
Boxing promoter Eddie Hearn has opened up on Anthony Joshua ahead of his blockbuster fight with Francis Ngannou
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Joshua has since proceeded to return to winning ways, however, emphatically beating Jermaine Franklin Jr, Robert Helenius and Otto Wallin over the past year.
Hearn, speaking on Ariel Helwani’s MMA Hour, has lavished praise on the Watford-born boxer.
And the 44-year-old has revealed he was stunned by what he saw behind the scenes prior to Joshua's victory over Wallin in December.
“I can’t tell you how much I believe AJ is gonna beat Francis Ngannou and then he is going to beat the winner of Fury vs Usyk, and he’s going to become undisputed heavyweight world champion," he said.
"I see a side of him that I haven’t seen for so long.
“Before he fought Otto Wallin, I went in the changing rooms and he was hitting pads with Ben Davison, and I was ‘oh my God, he’s back and I’ve never seen anything like it’.
"Punching with ferocity, confidence, tactically completely on the same wavelength with Ben Davison.
“I hoped it would translate in the performance, and it did.
"Now we’re gonna see – it’s a week on Friday, two giants will meet in the ring in Riyadh. And when you say giants, this is the first time AJ has fought an opponent that’s outsized him.
“This guy is huge. When I turned to him at the press conference and starting talking to him, and then I turned to AJ, it was like a cruiserweight and a heavyweight.
"So this is a real threat. This is Godzilla and King Kong – two ginormous men and anything can happen in this fight.”
Joshua has been criticised by some for taking the bout with Ngannou.
Ngannou has just one career fight to his name in boxing so far, which he lost narrowly against Tyson Fury back in October.
But Hearn insists the 37-year-old is dangerous and claims Joshua is taking the fight seriously.
“When I went to the gym the other day to see AJ, he is taking this like Tyson Fury x 10, he’s taking this fight so seriously," he added.
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Anthony Joshua and Francis Ngannou will fight in Saudi Arabia on March 8
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"Frank Warren talks about the jeopardy in this fight – that’s a great word for this fight.
"Because if you get beat, you’ve got beaten by a 0-1 guy.
“But when Turki Alalshikh, His Excellency says the winner of this fight will go on and fight for undisputed against the winner of Fury and Usyk, that to us is a dream chance because we’ve chased that for so long.”
Meanwhile, Hearn also believes Ngannou will quit boxing for a return to MMA if he's able to beat Joshua.
"I think if he gets destroyed by AJ, I think he will fight in MMA," Hearn predicted.
Anthony Joshua has won his last three fights since losing to Oleksandr Usyk in 2022
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"I think if it’s competitive, certainly if he wins, he’ll go on and potentially fight Tyson Fury.
"This fight is going to tell us a lot because every time I talk to you, I get very scared, and I just get a feeling in my stomach because I know you think he can win this fight."