Former world number one Simona Halep withdrew ahead of her second round match at the Western & Southern Open on Wednesday with a "small tear" to her right adductor in the latest injury setback for the Romanian.
Halep, who missed the French Open and Wimbledon due to a left calf tear, looked like she might not make it through her first round match on Tuesday after she needed a medical time out to attend to her right leg.
She came back and managed to battle through the discomfort to defeat Magda Linette 6-4 3-6 6-1 but a scan revealed it would be unwise to continue.
"Unfortunately, a scan this morning showed that I have a small tear in my right adductor and therefore it would be too risky for me to play tonight," she tweeted ahead of her match against Jessica Pegula at the tournament in Cincinnati.
Halep, 29, said she would rest up and do everything she can to be ready for the upcoming U.S. Open in New York, where she will look to claim her third Grand Slam title.
"To the fans in Cincy, it was beautiful to see you again," she said.
(Reporting by Rory Carroll in Los Angeles; Editing by Stephen Coates)