Tyson Fury has been told by his own father that he must change his approach or Oleksandr Usyk could make a 'fool' out of him.
John Fury is still backing his son to win in Riyadh next month but insists he must up his performance from his last fight against Francis Ngannou.
Fury and Usyk will put their belts on the line in a huge undisputed bout in Saudi Arabia on February 17.
Both fighters are unbeaten in their professional career and will look to put years of trash talk behind them.
Tyson Fury has been sent a warning by his father ahead of the Oleksandr Usyk fight
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Fury senior knows it will be one of the toughest tests his son has faced so far.
He says the 35-year-old cannot afford to box like he did in his trilogy against Deontay Wilder or the narrow win over MMA star Ngannou.
John Fury told the Daily Mail: "That style he had for those three fights against Wilder will not beat Usyk. They're two different people.
"Usyk is a class boxer. He's tricky, his coordination is good, his movement is good, he leans out of the way of punches and he's hard to pin down.
"If you can't set traps and pose problems for a man like Oleksandr Usyk, he's just going to make a fool out of you in the ring.
"At the end of the day, that straight-up Kronk style, what he [Tyson] was doing with Francis Ngannou won't work against Usyk.
"Ngannou wouldn't have been able to land a glove on the old Tyson.
"That style they've got only worked against Wilder because Wilder is a one-trick pony.
"Wilder couldn't box going back, Wilder couldn't box full stop. Wilder was there to be hit. All Wilder had in his arsenal was a big punch and bravery.
"He was a brave man with a big punch. But, that style [Tyson's style], you wouldn't need to be a brain surgeon to work it out.
"It's no good living off your morals on those wins."
Fury senior says his son will work off 'instinct' against Usyk if his tactics don't start well.
He added: "You're fighting a man with different intellect here.
"You're fighting a man with brains. He's a very intelligent man and so is his team.
"They've got to make some major adjustments to Tyson's camp. Luckily, Tyson can win on a bad night.
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John Fury says Tyson must change his approach for the Oleksandr Usyk fight
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"He will just revert back to what he wants to do anyway.
"If things aren't going well, he will revert back to what he does best. It's instinct."
He also hit out at Fury's camp for their preparation for the fight against Ngannou.
John Fury added: "Last time, Tyson's camp was an absolute joke.
"What they were doing for 12 weeks, I have no idea. Lets hope it's different this time.
Tyson Fury and Oleksandr Usyk will battle it out in February
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"Obviously I don't know because I am not out there. What I say is irrelevant now, they [Tyson and Usyk] are going to fight anyway.
"But, lets put it this way. The man with the best team, the man that has prepared the best, will win the fight on the night."