Wladimir Klitschko's world title defence against Tyson Fury has been postponed after the champion suffered a calf injury.
WBA Super, WBO and IBF king Klitschko, who recently returned to his training camp in Austria after Wednesday's eventful press conference in London, has pulled out of the October 24 clash due to the problem.
Klitschko said: "Especially after the exciting press conference last Wednesday, I was looking forward to this fight very much. I know that a lot of fans have already organised their trips to support me in Dusseldorf.
I apologise to my opponent, who has spent many weeks preparing for this fight. I will do my very best to recover as fast as possible.
"I am so sorry that I am not able to fight on October 24. I also apologise to my opponent, who has spent many weeks preparing for this fight. I will do my very best to recover as fast as possible."
Leading German physician Dr Hans-Wilhelm Müller-Wohlfahrt said: "The clinical and MRI-examination showed a partial musculotendinous tear of the left calf.
"The boxing fight planned for October 24 (World Championship in the heavyweight division) should be postponed for an indefinite period of time. Due to this injury we strictly recommend ceasing athletic activity in the next weeks."
The unbeaten challenger's reaction was swift, as he posted on social media: "Well it's official @Klitschko has pull (sic) out of the fight with an injury in his leg, it's a bit funny as I predicted this would happen!!!
"Don't feel sorry for me I'll b (sic) ok, I'm sorry for the fans again as they are the biggest losers hear. Flights & hotels travel, sorry guys."
The 39-year-old Ukrainian (64-3-KO53) has not tasted defeat for more than 11 years but many feel Fury (24-0-KO18) represents his biggest test and the Mancunian was certainly full of confidence when the pair came face to face earlier in the week.
Arriving as Batman, Fury put on a press conference for the ages - wrestling The Joker to the floor and then dominating the verbal exchanges before threatening to fight Klitschko there and then for calling him "a clown".
The champion repeated his threat to put Fury through "therapy" but struggled to make himself heard with Fury's father, John, interjecting regularly and the challenger's boisterous entourage making themselves heard too.
Further details regarding the Sky Sports Box Office event will be announced in due course.