The 29-year-old Uzbek tore the Achilles tendon of his left leg last week in training.
As a consequence, Chagaev had to pull out of his fight against Russia’s Nikolay Valuev, which had been due to take place in Halle, Germany, on Saturday.
Chagaev, who is expected to be back to full fitness by the end of the year, must defend his WBA title by June 26th 2009.