Williams will lose her number one ranking on Monday
Serena Williams has been forced to withdraw from this week's WTA tournament in Linz where she had been due to make her comeback from injury.
The 29-year-old has been sidelined since July with a foot injury she picked up after standing on broken glass in a Munich restaurant.
Williams had been cleared by her doctor to return to competition.
But the American suffered "a physical problem" which surfaced in her final training session for the event.
Instead of travelling to the Austrian city on Sunday, Williams chose to undergo further medical tests and later announced her withdrawal.
A comeback at the modest Linz tournament would have allowed Williams get herself in condition for the Masters in Doha at the end of October, which is played on the same surface.
Williams will lose her world number one spot when the latest WTA rankings are published on Monday, after 20-year-old Dane Caroline Wozniacki secured top spot by reaching the quarter-finals at the Beijing tournament.
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