David Haye has been forced to postpone his rematch with Tony Bellew after tearing his biceps during training.
The injury-prone heavyweight, 37, has withdrawn from the match-up scheduled for December 17 at London's O2 Arena but is not considering retirement and hopes to instead fight his rival on March 24 or May 5.
"I am devastated to announce my much-anticipated rematch against Tony Bellew has been postponed until Match 24 or May 5, subject to scheduling," Haye said.
"Despite the recent injury rumours, I was in perfect condition with an incredibly strong training camp, weighing lighter than I have for more than five years, I couldn't wait to get back in the ring. I was ready to rewrite the ending of the Haye-Bellew saga."
What Haye described as a "freak accident" occurred last Thursday, and led to a procedure on Monday afternoon that he insists has been successful.
"After a freak accident during a stair conditioning session, which I've done with no incident hundreds of times, I lost my footing and slipped," he said.
"So I instinctively grabbed the banister to stop myself toppling down the stairwell, in doing so I somehow managed to damage my biceps in the process.
"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."
The injury is only the latest Haye has suffered. He fought on despite rupturing his Achilles during the dramatic defeat by Bellew in March, his third fight - and first against a reputable opponent - since returning to the ring after a near four-year absence in January 2016.
He had previously announced his retirement because of a shoulder injury he sustained in the build-up to a scheduled fight with Tyson Fury, having first been forced to postpone that after being cut during sparring.
The Fury fight had been scheduled after Haye's withdrawal, owing to a hand injury, from an earlier match-up with Manuel Charr, and four years after a back injury led to the cancellation of a fight with Wladimir Klitschko in the summer of 2009.
Haye had returned against the little-known Mark de Mori at a career-heaviest 16st 3lbs, despite being widely considered a natural cruiserweight, and insisting he required the additional bulk to prevent further injuries.
Since the defeat by Bellew and Achilles injury he has split with trainer Shane McGuigan and begun to work with Cuban Ismael Salas.
"I'm gutted the rematch has been postponed, both for myself but more for the fans," said Bellew, 34. "I've had a tough camp with a lot going on in my life but was ready to repeat my win.
"I'll get over this disappointment over Christmas with my family and will be straight back into camp for a new date. It's a big disappointment."
Despite former world heavyweight champion Fury remaining without a boxing licence and awaiting a new date for his hearing with UK Anti-Doping after two years of inactivity, he posted a video on social media in which he claimed he would be "ready, willing and waiting" to fight Bellew on May 5.