Frank Warren, promoter for light heavyweight contender Callum Johnson, has confirmed that his boxer has withdrawn from his upcoming fight - after testing positive for COVID-19.
Johnson was scheduled to challenge WBO light heavyweight champion Joe Smith in New York, in an ESPN televised main event on January 15.
"It's a real great shame for Callum," promoter Frank Warren told BBC Sport.
"Hopefully we can get him back in, they may want to [reschedule the fight] in late spring. He worked really hard to get the opportunity."
Smith is still expected to fight on the card with a late replacement being finalized shortly.
It might be tough for Johnson to reschedule the fight - because one of Warren's other light heavyweights, Anthony Yarde, is the mandatory challenger and plans to press for his title shot.
Yarde, who is number one in the WBO's rankings, secured the shot last month when he knocked out Lyndon Arthur.
"If Callum doesn't get his shot then Anthony Yarde is next," Warren said.
"I'd love to do Joe Smith v Anthony Yarde in the UK. The WBO say there is a mandatory due and it's going to be Yarde. He is the number one. Anthony looked so good in his last fight against Lyndon Arthur. We've got him down to fight sometime in March anyway. Fingers crossed.
"We'll see what happens next week with Smith and how he comes through. Then go from there. I want to keep Anthony busy. We want to get the world title shot for him. The experience he's gained since [fighting] Sergey Kovalev stands him in good stead. He really gives Smith so many problems."