Oleksandr Usyk's manager, Alexander Krassyuk, has raised suspicions over whether Tyson Fury trained prior to his win over Francis Ngannou back in October.
Fury was unconvincing in Saudi Arabia that evening, with Ngannou knocking the 35-year-old down in round three of that bout.
Ngannou proceeded to face Anthony Joshua earlier this month.
And the former UFC star lasted just two rounds, with AJ knocking his opponent down three times on his way to victory.
Tyson Fury is currently preparing for his huge showdown with Oleksandr Usyk in May
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The dominant nature of Joshua's win has seen Fury scrutinised, with many questioning whether he trained given how AJ easily swept his opponent aside.
And Krassyuk, speaking to World Boxing News, has now raised suspicions over whether the 35-year-old put in the work prior to their contest taking place.
“For the Ngannou fight, I am sure Fury did not train, but AJ did," he said.
“Although you can’t estimate the real level of performance of two boxers with the third guy.
“The only answer to the question of Fury and Joshua is to see a head-to-head fight. Only that can give an answer.”
After the win, Hearn boldly claimed that Joshua was the best heavyweight on the planet at the current moment in time.
Fury hit back at that statement by saying Usyk would likely have 'something to say about that'.
And Krassyuk has shrugged off Hearn's comments, admitting he feels British promoters are too quick to praise their man without looking at the bigger picture.
“I did smile because I was glad to see my friend Eddie being so happy," he said when asked about Hearn's praise for Joshua.
"I think Eddie was sincere because he really considers AJ to be number one.
"It does not mean he really is, but AJ is a great champ and a very nice man.
“One thing is clear, though. Some of the elite British heavyweight fighters are a bit overestimated by their respective promoters and fans.”
Krassyuk did, however, hail Joshua for his performance - insisting the Watford-born star was 'brutal' as he powered his way past Ngannou.
"That was a brutal act," he continued.
"But it was well expected as the boxer was fighting an athlete from another sport.
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Alex Krassyuk believes Oleksandr Usyk is the best heavyweight in the world ahead of Tyson Fury fight
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“Even though MMA is a combat sport, chances are very little to see the real competition. Only Tyson Fury’s fight made the exception.
"But now we know that Tyson Fury could not sleep for three nights, and his performance appeared to be that ugly.”
Fury vs Usyk is set to take place in May 18.
Yet Krassyuk, speaking to the same publication, insists there's 'no guarantee' the fight will happen on that date.
“Theoretically, the rematch should happen before the end of 2024," he said.
Tyson Fury looks in great shape ahead of his blockbuster bout with Oleksandr Usyk
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"However, we all know that Tyson is not the world’s best’ rematch-er.
“And after he loses to Usyk in the first bout, you cannot predict his behaviour at all.
“I say this, but I have no guarantee that the first fight ever takes place.
"The man has withdrawn four times in a row already. We have even decided to stop all the jokes and criticisms towards Luke [Tyson Luke Fury] to support his confidence.
"So if there is anything else we can do to help him get in the ring with Usyk, we are ready to do that.”