Agnieszka Radwanska of Poland in action against Maria Sharapova of Russia, during the singles round match of the BNP Paribas WTA Finals 2014 at the Singapore Indoor Stadium, in Singapore, 24 October 2014. EPA/WALLACE WOON

Maria Sharapova of Russia reacts in her match against Agnieszka Radwanska of Poland, in their singles round match of the BNP Paribas WTA Finals 2014 at the Singapore Indoor Stadium, in Singapore, 24 October 2014. EPA/WALLACE WOON

Simona Halep of Romania in action against Ana Ivanovic of Serbia during their singles Round Robin match of the BNP Paribus WTA Finals 2014 at the Singapore Indoor Stadium, 24 October 2014. EPA/WALLACE WOON

Caroline Wozniacki of Denmark reacts after winning against Petra Kvitova of the Czech Republic during their singles Round Robin match of the BNP Paribus WTA Finals 2014 at the Singapore Indoor Stadium, 24 October 2014. EPA/WALLACE WOON

Ana Ivanovic of Serbia in action against Simona Halep of Romania during their singles Round Robin match of the BNP Paribus WTA Finals 2014 at the Singapore Indoor Stadium, 24 October 2014. EPA/WALLACE WOON