Klitschko (left) has a back injury but should be fit to fight within 60 days
IBF and WBO heavyweight champion Wladimir Klitschko has pulled out of Saturday's world title bout with Dereck Chisora because of a stomach injury.
The 34-year-old Ukrainian was due to take on 26-year-old Londoner Chisora in Mannheim, Germany, and it is still hoped they could fight early next year.
"Wladimir has withdrawn from the fight. He has torn a muscle in his back," said Klitschko's US advisor Shelley Finkel.
"It is not too serious. He should be able to fight again within 60 days."
Chisora was sceptical about the seriousness of Klitschko's injury, telling BBC Radio 5 live: "When we saw him this afternoon he was all right, everything was good, he was moving all right and I just think he didn't want it.
"He could see I was in my stride, my face didn't look tired, I was chilled - he saw that when I was in the ring.
"This was a nightmare for him basically and he had to get out, but now he's out we can't complain."
Talks are now expected between the fighters' representatives with a view to rescheduling the bout, although WBA champion David Haye could see this as his chance to renegotiate a deal with Klitschko about a possible unification fight.
Klitschko was set to fight WBA champion Haye last year before the Englishman pulled out with a back injury and negotiations have repeatedly stalled since then.
Haye has also talked about fighting Wladimir's older brother Vitali, who is the WBC champion.
Unbeaten Chisora's last fight was a ninth-round stoppage of Norwich's Sam Sexton on 18 September, while Klitschko knocked out Nigeria's Sam Peter in the 10th round a week earlier.