Australian Open: Serena Williams discusses back injury
Serena Williams says she should "probably" have pulled out of her fourth round Australian Open defeat by Ana Ivanovic with a back injury.
The world number one reveals she has been struggling with the problem for a "few days" and can play "ten times better" than she did in Melbourne.
Former world number one and 2008 French Open champion Ivanovic fought back from a set down to win 4-6 6-3 6-3 - her first ever victory over Williams in five attempts.
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