Serbian Novak Djokovic, winner of the 2011 U.S. Open, has announced that he is withdrawing from the the Shanghai Masters due to a nagging back muscle injury. Djokovic, the world's top-ranked male tennis player, was also forced out of play of the recent China Open due to his back ailment which has been diagnosed as a partial rupture of a back muscle.
Djokovic has reportedly not recovered from the injury he sustained in winning the U.S. Open against Spain's Rafael Nadal on Sept. 12.
Djokovic says he "did another check this week and the results are not good. I need to continue my rehabilitation.''