Dereck Chisora has withdrawn from Saturday's fight against Tyson Fury after fracturing his hand in training.
The pair had been due to meet in Manchester for the British and European heavyweight titles.
Chisora, 30, said: "I can't tell you how disappointed I am but it is on the advice of my specialist I do this."
The fight had been billed as an eliminator for the right to meet IBF, WBA and WBO heavyweight champion Wladimir Klitschko.
Chisora promised the bout would go ahead at a later date, adding: "I'm sorry for the fans who will miss this great fight between me and Tyson on Saturday.
"But once my hand is healed and I'm given the all-clear to train and punch again, I'll be working on the new date for the fight."
Meanwhile, the British Boxing Board of Control has opened a misconduct hearing against Fury, 25, for a foul-mouthed tirade against Chisora at a promotional news conference.
However, Fury claimed he had no intention of attending the hearing on 13 August and said he will approach the Boxing Union of Ireland if his British licence is suspended.
The fighter, who represented both England and Ireland at amateur level, said: "If they want to ban me and keep being fools, I will just go and get a BUI licence and box out of Ireland."
He added: "I am sick of them picking on me all the time. It's crazy."
Fury and Chisora have fought once before, with Fury winning on points at Wembley Arena in 2011.
Saturday's show at Manchester Arena will still go ahead with Britain's Billy Joe Saunders now the main event as he challenges Italy's Emanuele Blandamura for the vacant European middleweight title.