( CNN ) -- Petra Kvitova dumped Caroline Wozniacki out of the WTA Championships with a straight sets victory that sealed her place in the final four . Kvitova , the 2011 Wimbledon champion , inflicted Wozniacki 's second defeat in Istanbul , winning 6-4 6-2 to go top of the Red Group . World number one Wozniacki , who called the trainer on during her match after complaining of feeling sick , is rock bottom of the group after playing all three of her round robin games . After her victory Kvitova told CNN she was delighted to make the final four : `` It 's nice when I win and I 'm happy to be in the semi-final . Istanbul is a great place and it is great experience for me . `` I have had a great season and it 's very nice to play here -- it 's like something new for me as I 'm still learning . I am enjoying every match I play and I 'm trying not to think about winning here . '' Wozniacki told reporters : `` I tried my best , but my body did n't want to do the things I asked it today . What I told my brain did n't go to my body . `` It 's just unfortunate that my body has been feeling tired . To get sick now is not the best time if you want to beat the top players . '' Czech Kvitova faces Agnieszka Radwanska on Friday -- a match that will determine who grabs the second qualification spot in the red group . Radwanska , from Poland , currently occupies second spot after she saved three match points to beat Russia 's Vera Zvonareva 1-6 6-2 7-5 . The Pole can make sure of her place in the semis as long as she wins a set in her clash with Kvitova . In the white group , Victoria Azarenka sealed her spot in the last four after beating China 's Li Na 6-2 6-2 . The Belarusian added to her victory over Australia 's Sam Stosur to ensure her meeting with Marion Bartoli , who replaced the injured Maria Sharapova , is academic . Azarenka told the WTA 's official web site : `` Li Na has such a good return and likes to dominate from the beginning , so I tried to serve well and take that away from her . `` The crowd here in Istanbul just makes me want to play well and show them some good tennis . They 're a fantastic crowd and make me want to play really well . '' The final qualification spot in the white group will go to the winner of Friday 's clash between Li Na and Stosur .
Petra Fernández beats Caroline Garcia to make semis at WTA Finals . Kvitova wins 6 - 4 6 - 2 to knock world No.1 Woznaicki out of competition . Victoria Azarenka joins Kvitova in the final four after beating China 's Li Na . Agnieszka Radwanska beats Vera Zvonareva to keep hopes of semi ##s alive .