David Haye's heavyweight rematch with Tony Bellew has been postponed after Haye slipped on the stairs in a "freak" training mishap.
Haye, who has had surgery for a torn biceps, said he was "devastated".
WBC cruiserweight world champion and fellow Briton Bellew, 34, stopped former heavyweight world champion Haye, 37, in the 11th round in March.
The rematch, a sell-out scheduled for December 17 at the 02 Arena in London, will be held on March 24 or May 5, 2018.
Haye suffered the injury during training on November 16.
"After a freak mishap during a stair conditioning session, which I've done with no incident hundreds of times, I lost my footing and slipped," he said.
"I instinctively grabbed the banister to stop myself toppling down the stairwell. In doing so I somehow managed to damage my biceps.
"I underwent a procedure to repair it; this was pretty straightforward and my doctor and physiotherapist have no doubt that not only will I make a full recovery but will be able to be back in the gym to start my arm rehabilitation in two weeks.
"I would like to apologise to Tony, his family and his training team, as well as all our fans who have been left disappointed."
Haye last month had compared Bellew's win over him in March to "robbing a bank" and predicted a revenge victory in December.
But Bellew said: "I didn't rob a bank - I got in the boxing ring and punched him senseless then I went home."
He added: "On 17 December I will turn up and I will win again."
Former WBA heavyweight champion Haye needed surgery following the defeat by the 34-year-old, and has since split with trainer Shane McGuigan to join Cuban coach Ismael Salas.
The Londoner questioned Bellew's motivation for their rematch after he reportedly earned £2.8m from their first encounter.
"People rob banks to secure their family," Haye said.
"Would you go back to rob that same bank again? Is your hatred so bad for the clerk behind the desk that you need to do it again?
"I know what Tony earned for the first fight and he is financially secure for the rest of his life. He's a multi-millionaire and that's fantastic.
"He's got into a very small club of British boxers who have enough money that don't have to box, don't have to have a job. So I ask myself "what are his motivations going into the second fight?'."
"I've got a screw loose - I like having a fight."
*DOWN AND OUT: Haye stopped in Round 11 during the clash in March.
*Another shot taken during the Haye/Bellew clash.