Tyson Fury only needs to be at 80 per cent to beat Deontay Wilder '“ Frank Warren

Fury challenges WBC heavyweight champion Wilder at Los Angeles’ Staples Center tomorrow night in a fight that has been years in the making.

The heavyweight has followed over two-and-a-half years of inactivity, during which he admitted to taking cocaine and ate and drank to such excess that he swelled to an estimated 27 stones, with only 14 unremarkable rounds against little-known opposition.

Despite being only 30 and rarely being involved in tough fights, the potential physical toll involved in doing so would prove damaging for even the most naturally gifted athletes, particularly in the harshest of sports.

Those 14 rounds against Sefer Seferi and Francesco Pianeta may also have done little to shift the ring-rust Fury would have accumulated since defeating Klitschko three years ago this week and Warren, his experienced promoter, said: “The only question is if Tyson has it in him to do what he did in the past.

“We don’t know that, nobody knows that, because we haven’t seen it yet.

“The big question mark is how has this time out of the ring affected him? He’s had two easy wins, two comeback fights; two fights where he trained to make the weight rather than train for a fight. He has lost 10 stones, that is a lot of weight, what does he have left?

“If he is 80 per cent of what he was, he beats this guy. Who is the better boxer out of the two of them? One is a far more accomplished boxer, it is very smart the way he fights. He is a very, very intelligent boxer and one of the most difficult to fight.

“He’s a switch-hitter, he goes from side-to-side, he avoids shots well, he leans back, he tucks his chin under his shoulder. What Wilder matches him for is speed; they are both fast.

“He is a boxing encyclopedia. He is an exponent of the art of boxing; he is a boxing historian, he can tell you anything about anybody’s style, I respect him for that.”

Warren also insists that the winner of tomorrow night’s fight in Los Angeles will be established as the division’s leading fighter, beyond Anthony Joshua, the reigning IBF, WBA and WBO champion.

“Whoever wins this, they are the No 1,” the 66-year-old said. “Anthony Joshua is in the slipstream.

“They had the balls to stand up and make the fight; they did what he wouldn’t do and we all know (Joshua’s) next fight is going to be against (Dillian) Whyte if he beats (Dereck) Chisora.

“If Tyson were to lose and I don’t think he will, it’s how he loses and then did he take this fight too quickly, or should he have had a couple more fights first? Because the plan when he came back was to have four fights.”