Petra Kvitova forced out
Defending champion Petra Kvitova has been forced to pull out of the ongoing WTA Championships due to illness.
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Last year's Wimbledon winner cited a viral illness for her withdrawal on Wednesday morning.
She will be replaced in the Istanbul tournament by alternate Sam Stosur, the former US Open champion.
Kvitova was out of sorts during her opening group match at the season-ending event on Tuesday, losing in straight-sets to Agnieszka Radwanska. It was her first defeat on an indoor hardcourt for two years.
The news is not good for the Czech Republic, whose Fed Cup final with Serbia is less than two weeks away.
Stosur will now take Kvitova's place for matches against Maria Sharapova and Sara Errani.
The Australian's first match will be on Thursday.