Maria Sharapova and Madison Keys have withdrawn from next week`s Nature Valley Classic in Birmingham as they look to regain full fitness ahead of Wimbledon.
Sharapova, the 2004 Wimbledon champion, said she needed rest after reaching the French Open quarter-finals.
The 31-year-old Russian served a doping ban in 2016 and was forced to skip the grass-court season last year with a thigh injury.
"I need to take care of my body and make sure I stay healthy," Sharapova said in a statement. "Sometimes that means you have to take tough decisions like this one."
American Keys, 23, will miss the Birmingham event due to an abdominal injury.