Defending champion Agnieszka Radwanska withdrew from the Tianjin Open with a right thigh injury on Thursday, shortly after beating Evgeniya Rodina 6-1, 6-1 to reach the quarterfinals.
Radwanska said she pulled out to give herself time to fully recover before the WTA Finals in Singapore later this month.
“It’s the end of the season, I guess everyone is struggling with something,” she said in comments posted on the WTA website.
Radwanska broke Rodina five times and won all but four points on her first serve. She had won her last eight matches, starting with her run to the China Open title last week.
Radwanska’s withdrawal allows Chinese veteran Peng Shuai to advance to the semifinals. Peng beat Chang Kai-Chen 6-3, 6-2.
Olympic gold medallist Monica Puig also reached the quarterfinals, beating Lara Arruabarrena 6-4, 6-2, while Alison Riske defeated Magda Linette 6-3, 7-6 (2).