Jana Cepelova, of Slovakia reacts as she loses a point to Magdalena Rybarikova, of Slovakia, during their tennis match at the Citi Open Tennis tournament, Thursday, Aug. 2, 2012, in Washington. Rybarikova defeated Cepelova 6-2, 6-4 in a quarterfinal match. (AP Photo/Richard Lipski)

Magdalena Rybarikova, of Slovakia, serves to Jana Cepelova, of Slovakia, during their match at the Citi Open tennis tournament, Thursday, Aug. 2, 2012, in Washington. Rybarikova defeated Cepelova 6-2, 6-4 in the quarterfinals match. (AP Photo/Richard Lipski)

Magdalena Rybarikova, of Slovakia, returns a volley to Jana Cepelova, of Slovakia, at the Citi Open tennis tournament, Thursday, Aug. 2, 2012, in Washington. Rybarikova defeated Cepelova 6-2, 6-4. (AP Photo/Richard Lipski)

Magdalena Rybarikova, of Slovakia, returns volley to Jana Cepelova, of Slovakia, during their match at the Citi Open tennis tournament, Thursday, Aug. 2, 2012, in Washington. Rybarikova defeated Cepelova 6-2, 6-4 in their quarterfinals match. (AP Photo/Richard Lipski)

Anastasia Pavlyuchenkova, of Russia, returns the ball to Kai-Chen Chang, of Taiwan, during a quarterfinal of the Citi Open tennis tournament, Thursday, Aug. 2, 2012, in Washington. Pavlyuchenkova won 6-4, 6-4. (AP Photo/Richard Lipski)

Kai-Chen Chang, of Taiwan, returns volley to Anastasia Pavlyuchenkova, of Russia, during their match at the Citi Open tennis tournament, Thursday, Aug. 2, 2012, in Washington. Pavlyuchenkova defeated Chang 6-4, 6-4 during their quarterfinals match. (AP Photo/Richard Lipski)

Coco Vandeweghe serves to Vania King during their match at the Citi Open tennis tournament, Thursday, Aug. 2, 2012, in Washington. King defeated Vandeweghe 6-1, 3-6, 6-4 during their quarterfinal match. (AP Photo/Richard Lipski)

Coco Vandeweghe wipes her face with a towel during her quarterfinal match against Vania King at the Citi Open tennis tournament, Thursday, Aug. 2, 2012, in Washington. King defeated Vandeweghe 6-1, 3-6, 6-4. (AP Photo/Richard Lipski)

Vania King returns volley to Coco Vandeweghe during their match at the Citi Open tennis tournament, Thursday, Aug. 2, 2012, in Washington. King defeated Vandeweghe 6-1, 3-6, 6-4 during their quarterfinals match. (AP Photo/Richard Lipski)

Coco Vandeweghe serves opponent Vania King during their match at the Citi Open tennis tournament, Thursday, Aug. 2, 2012, in Washington. King defeated Vandeweghe 6-1, 3-6, 6-4 during their quarterfinals match. (AP Photo/Richard Lipski)

Vania King returns volley from Coco Vandeweghe during their match at the Citi Open tennis tournament, Thursday, Aug. 2, 2012, in Washington. King defeated Vandeweghe 6-1, 3-6, 6-4 during their quarterfinals match. (AP Photo/Richard Lipski)

Eugenie Bouchard returns volley to Sloane Stephens during their match at the Citi Open tennis tournament, Thursday, Aug. 2, 2012, in Washington. (AP Photo/Richard Lipski)

Eugenie Bouchard volleys back to Sloane Stephens during their match at the Citi Open tennis tournament, Thursday, Aug. 2, 2012, in Washington. (AP Photo/Richard Lipski)