This is the second time the rematch between Tyson Fury and Wladimir Klitschko will be postponed, with the British boxer pulling out due to injury.
The undefeated heavyweight champion was slated to fight the Ukrainian come October 29 in defence of his WBO and WBA belts.
However, having pulled out of the original July 9 date due to an ankle injury, he is citing that same reason for his inability to fight.
Fury’s management team Hennessy Sports confirmed the news in a statement released on Friday night.
“It is with the deepest regret that we have to announce that the world heavyweight championship rematch between Tyson Fury and Wladimir Klitschko, scheduled to take place on the 29th October 2016 at the Manchester Arena, will not be going ahead,” said Hennessy Sports.
“Tyson has, this week, been declared medically unfit to fight. Medical specialists have advised that the condition is too severe to allow him to participate in the rematch and that he will require treatment before going back into the ring. Tyson will now immediately undergo the treatment he needs to make a full recovery.
“We and Tyson wish to express our sincerest apologies to all those concerned with the event and all the boxing fans who had been looking forward to the rematch. Tyson is understandably devastated by the development.
“We will be making a further statement in due course. Until then, we ask that Tyson and his family be given the privacy and the space he needs to recover during this difficult time.”
Fury (25-0-KO18) claimed a shock points’ win over Klitschko (64-4-KO53) to claim the WBA Super, WBO and IBF titles in November last year.
WBA president Gilberto Mendoza said his organisation would look into the reason for Fury’s withdrawal.
“I heard the news,” Mendoza told Sky Sports Richard Damerell. “I have not received anything official from Tyson Fury’s camp.
“Let’s see what happens. I think we’re going to enquire with Tyson Fury to see what has happened.”