World heavyweight champion Vitali Klitschko's April title defence against Hasim Rahman has been postponed because of a thigh injury to the Ukrainian. The World Boxing Council (WBC) fight was scheduled to take place at New York's Madison Square Garden on April 30 but organisers are now considering a date in June. Klitschko retained his WBC heavyweight crown last December when he stopped Britain's Danny Williams in the eighth round at the Mandalay Bay Resort and Casino in Las Vegas. It was the Ukrainian's first defence of a title he won in April when he beat South African Corrie Sanders.