Promoter Eddie Hearn says he is now considering a “plan B” for Anthony Joshua and that Tyson Fury’s team must clarify by the end of the week whether the pair can still fight this summer.
Fury and Joshua had agreed to a super fight in Saudi Arabia on 14 August.
But on Monday it was ruled Fury must face American Deontay Wilder for a third time by 15 September.
Hearn – Joshua’s promoter – said the “game changed” with the ruling, adding: “We have to have a plan B in place”.
He added: “The one that springs to mind is the WBO mandatory – Oleksandr Usyk.”
Less than a week ago Hearn told BBC boxing correspondent Mike Costello he did not have any back-up plan in place because he was confident Joshua-Fury would be finalised.
And on Sunday, Fury announced he had agreed to the bout.
But Wilder’s team had long said they had contractual rights to a third fight with Fury, and on Monday a US judge ruled in arbitration that the pair must fight again by 15 September.
The deadline means Fury’s team are likely to consider paying Wilder to step aside but there are no guarantees the former world heavyweight champion will accept a deal to do so.
“This negotiation has been going on for three or four months and we were always assured this wouldn’t be a problem,” Heard added.
“It was very strange decision from the arbitrator to say the least, but that’s their business.
“We can’t control that or be involved with that process. As far as I understand it, Fury wants to fight Joshua. Hopefully they can resolve the issue and we move forward but over to them.
“We have provided an unbelievable opportunity to Fury. We want to be in a position by the end of the week to know are we fighting Fury or moving forward with another option.
“It’s exciting, it’s disappointing and it’s boxing. Let’s see if Team Fury can pull something out of the bag for their fighter. I think he will be disappointed.”
Ukraine’s Usyk – who has 18 wins from 18 bouts – holds the mandatory challenger position for Joshua’s WBO title.
Joshua was set to risk his WBO, WBA and IBF belts against WBC champion Fury in boxing’s first heavyweight contest for all four recognised world titles.
More to follow.