BEIJING, China - WTA Rising Star CoCo Vandeweghe was in the midst of a solid week at theDongfeng Motor Wuhan Open when she was suddenly felled by a left ankle injury in the quarterfinals. That problem reemerged on Sunday at the China Open against No.4 seed Agnieszka Radwanska, and the American had to retire in a second straight match, this time trailing the Pole, 6-3 ret.

It was always going to be a daunting day for Vandeweghe, who had never taken a set from her more experienced opponent in their three previous matches, including a decisive 6-4, 6-3 match in Beijing one year ago and another straight sets encounter at the Toray Pan Pacific Open earlier this fall.

The pair exchanged early breaks but the former World No.2 had established control over proceedings by the end of the opening set, breaking for a third time to close it out before Vandeweghe decided not to risk further injury by retiring.

Vandeweghe was one of four women to retire in a rough start to the China Open, top seed Simona Halep the biggest name among them - the Romanian was also troubled by a left ankle injury against WTA Rising Star Lara Arruabarrena. Lesia Tsurenko and WTA Rising Star Zarina Diyas also pulled the plug, each after losing the opening sets of their matches to Carla Suárez Navarro and WTA Rising StarMonica Puig, respectively.

Up next for Radwanska is the big-hitting Mona Barthel, who overcame Chinese wildcard Zhang Shuai in straight sets.