Beijing:India's Sania Mirza retired hurt from her first-round Olympic Games clash against Iveta Benesova of the Czech Republic on Monday.
Mirza, who only returned to the Tour in June after a three-month absence following surgery on her right wrist, was down 6-1, 2-1 when she pulled out.
"I've been feeling constant pain for the last two weeks," she said. "I've been on pain killers for the last six days. I took four this morning.
"It's unfortunate timing, it's very bad but there's nothing I can do."
The world number 26 said she would try to play the doubles tournament with partner Sunitha Rao.
The tournament had already been rocked by a series of withdrawals with top seed Ana Ivanovic joining the injury list on Sunday with a painful right thumb.
Fellow Serb Jelena Jankovic, who was confirmed as world number one on Monday, is also an injury doubt.
Russian star Maria Sharapova, Amelie Mauresmo and Tatiana Golovin had already pulled out while 1996 champion Lindsay Davenport has also ditched the singles with a nagging knee problem.
Mirza's retirement will temper Indian joy on the day shooter Abhinav Bindra won the country's first ever individual Olympic gold medal.