Oleksandr Usyk has a clause in his contract to replace Tyson Fury amid fears the Gypsy King could delay the fight again.
Usyk's coach says the Ukrainian will battle Filip Hrgovic on May 18 if the huge fight is postponed for a second time.
The pair were set to enter the ring in Riyadh, Saudi Arabia tonight in the first undisputed heavyweight fight since 1999.
However, Fury sustained a cut above his eye during a sparring session earlier this month and the fight was postponed.
Oleksandr Usyk has a clause to fight Filip Hrgovic if Tyson Fury delays the fight again
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A new date of May 18 was quickly arranged, giving Fury over three months to recover from the injury.
Fury has received widespread criticism from within the boxing fraternity, while Usyk's camp have also accused him of running from the 37-year-old.
Those claims have been shut down by Fury, who says he is determined to fight Usyk at least once.
But Usyk's coach Sergey Lapin says a plan is in place if his opponent pulls out again.
Croatian heavyweight Hrgovic doesn't have a next fight planned but he is waiting in the wings if Fury-Usyk doesn't go ahead.
Lapin told Fruity Slots: "I hope Usyk will get the chance to settle the score with Fury on May 18, but if he continues to run, then we have a clause in the agreement to replace Fury with Filip Hrgovic.
"Hrgovic is the back-up opponent, so the show will go on regardless of whether he shows up, this was also confirmed by His Excellency Turki Al Sheikh."
Either fighter would have to pay their opponent £10million from their contract if the fight is postponed again.
Lapin has full confidence his fighter will beat Fury if they do come to blows.
He added: "Let's say he did get cut - through a head guard and with large training gloves - can you imagine what will happen to his head when he receives a bomb from the Usyk in a ten-ounce glove?
"If Fury finally dares to enter the ring on May 18, then it will be a terrible dream for him, he has never boxed with a boxer of this level in his life.
"Ngannou exposed Fury for what he is, a fighter with too many miles on clock, a fighter who has had too many wars, and a fighter who is now in rapid decline to the point he's been badly troubled by sparring partners."
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Filip Hrgovic is in line to fight Oleksandr Usyk if Tyson Fury pulls out of the fight
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Lapin's comments come after Usyk's former trainer James Ali Bashir suggested that May is far too soon for Usyk to enter the ring again.
Ali Bashir believes Fury will need another couple of months at least for the cut to be fully healed.
He told Seconds Out: "From what I saw, it is going to take that cut six to seven months to heal.
"It seems like it is one of those cuts that needs to be stitched on the inside and on the outside to get the best result of healing.
Tyson Fury suffered a cut in a sparring session in early February
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"May, that’s cutting it short, that is hurrying it up. I can see that cut re-opening if they go in May.
"I would push the fight back to June or July to be sure. I personally as a boxing trainer would push it back.
"The longer that he takes time for it to heal, the better the cut is going to be but I don't know about May."
