The 34-year-old Klitschko had been a prohibitive favorite to retain his titles Saturday against the 26-year-old London native at the SAP Arena in Mannheim, Germany. Reports indicate there have been talks to reschedule the fight.
"The abdominal muscle is injured and therefore Wladimir Klitschko will not be able to fight on Saturday," said Dr. Sven Roessing, orthopedic specialist at the University Medical Center of Mannheim.
The injury is expected to sideline Klitschko four to six weeks.
It is the first time in Klitschko's professional career that he's withdrawn from a fight due to injury.