Maria Sharapova will not defend her title at the Australian Open next week after withdrawing from the year's opening grand slam tournament, officials said Sunday. The Russian world number nine advised tournament officials that she was not confident of her fitness levels after a shoulder surgery late last year. The 21-year-old was hindered by a right shoulder injury much of last season and skipped the Beijing Olympics and the US Open before having arthroscopic surgery in October. "I am very sorry to announce that I am not going to be able to defend my title at this year's Australian Open," Sharapova said in a Tennis Australia statement.