Top-seeded Agnieszka Radwanska has retired from her second-round match at the New Haven Open.
The world's second-ranked player, who received a bye in the first round, dropped her opening set 6-0 to Olga Govortsova, and was down 2-1 and a break in the second set when she ended the match.
A trainer was called in between sets to work on Radwanska's right shoulder, which has been bothering her this summer.
Earlier, Marion Bartoli rallied from three games down in the third set to beat American Sloan Stephens 6-1, 0-6, 6-3.
She will face fourth-seeded Sara Errani of Italy in the quarterfinals. Errani beat Carla Suarez Navarro of Spain 6-4, 6-3.
Germany's Mona Barthel withdrew from her match with seventh-seeded Maria Kirilenko of Russia because of a stomach disorder.