The 25-year-old Klitschko took a punch to the back of his left shoulder and immediately felt pain that stopped the sparring session.
An ultra sound scan and MRI revealed a torn muscle fiber in the shoulder and Klitschko was told he would be unable to fight for the next three to four weeks.
Klitschko captured the crown with a 12-round decision over Chris Byrd on October 14, 2000. He has retained the belt twice with victories over Derrik Jefferson in March and a sixth-round TKO of Charles Shufford in August.
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