As reported on Monday, David Haye has suffered a torn bicep, forcing him to postpone his heavyweight rematch with Tony Bellew.
The British pair were slated to do battle for a second time on December 17 at London's O2 Arena.
Bellew beat Haye at the same venue in March, aided by the former heavyweight world champion suffering a serious ankle injury mid-bout.
Haye said in a statement: "Despite the recent injury rumours, I was in perfect condition with an incredibly strong training camp, currently 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.
"Unfortunately, after a freak accident during a stair conditioning session, which I've done with no incident hundreds of times, I lost my footing, slipped, so instinctively grabbed the bannister to stop myself toppling down the stairwell, in doing so I somehow managed to damage my bicep in the process.
"This afternoon 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."
Haye suggested that the pair will attempt to reschedule the fight for March 24 or May 5 in 2018.
David Coldwell, trainer of Tony Bellew, says his boxer was devastated Haye's withdrawal.
"I'm just absolutely gutted. You can't really explain that sick feeling in your stomach and the look on Tony's face when he was telling me about… well, I was just gutted for him, absolutely gutted for him. He's still got to deal with loads and he's still got to go through loads as a fighter. This doesn't end for Tony Bellew right now but he's got to pick himself up and go again. He will," Coldwell told Sky Sports.
"He's gone through a lot in this camp. There's been a lot going on in his life and he just puts everything to one side when he walks into that gym, he's done his work and it has been the hardest camp he's been through. It just seems like it was all done for nothing. We are devastated. All the work you've done in the gym, the time you've had away from the family - the things you've missed out on your kids doing - it's all for nothing. Then you've just got to process, digest and then deal with it."
"Tony is a very strong-minded person and to be honest, what he has shown me in how he's dealt with everything going on in his life and was still preparing for this fight, my respect for him has gone up another level. Now let's see what's going to happen, what dates we're looking at and see where we go from there."