May 9 Serena Williams has pulled out of the Madrid Open with a thigh injury ahead of her quarter-final against Petra Kvitova, the world number one said on Friday.
Williams, winner of the last two editions of the tournament, suffered the injury in her first-round match against Belinda Bencic and with the French Open just two weeks away, she decided to pull out to give herself time to recover.
"I have a left thigh injury and, unfortunately, have to withdraw from this year's Madrid Open," the 32-year-old American said in a statement.
"It happened during my first-round match. It started to get better, but most importantly right now, I just need some time to rest and recover. It's beyond words. It's so frustrating...
"This is not the way I wanted this week to end."
The 17-times grand slam singles champion had been on a run of 15 consecutive victories on the Madrid clay and her victory over Carla Suarez Navarro in the last round brought up her 650th win on the women's tour.
(Writing by Toby Davis in London, editing by Ed Osmond; editing by xxx)