Former champion Lindsay Davenport, who has been struggling with a right knee injury, pulled out of Wimbledon on Thursday.
The American, winner here in 1999, had been due to face Argentina's Gisela Dulko in a second round match.
"It's been bothering me for a few weeks," Davenport said after her first round win on Tuesday, when she needed on court treatment for the problem.
The 32-year-old had returned to Wimbledon for this year's championships after a two-year absence.
