A file photograph of Serena Williams
Serena Williams has withdrawn from next week's Madrid Open, saying she wasn't ready to compete.
Tournament organizers say Williams withdrew because she needs more time to train before returning to action.
Williams, a 23-time Grand Slam champion, returned to the tour in Indian Wells this year after a 14-month absence because of the birth of her daughter.
She won in Madrid in 2012 and 2013.
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Williams was also scheduled to take part in a charity event in advance of the main tournament. Her place in the charity exhibition was taken by fellow American Coco Vandeweghe.
