WTA tennis champion Petra Kvitova has abandoned her title defence due to a viral illness, a day after losing her opening match in Istanbul to Agnieszka Radwanska.
The error-strewn, emotionally-fraught loss to the Pole in her opening group match had indicated there was something wrong with Kvitova's fitness.
Kvitova has been replaced in the season-ending top eight tournament by Australian Sam Stosur.
The former US Open champion can still qualify for the semi-finals if she wins the remaining two matches in the white group, against Maria Sharapova, the second seed, and Sara Errani, the French Open runner-up.