LONDON — Rafael Nadal withdrew on Friday from next week's grass-court tournament at Queen's Club because of knee trouble but hopes to defend his title at Wimbledon.

The top-ranked Spaniard is "struggling with ongoing knee problems and has been advised to rest by doctors," tournament organizers said in a statement.

"I have been having some problems in the past months with my knees, that's no secret, that did not allow me to compete always at 100 percent," Nadal said. "I need to work with my team to recover well, work on my physical condition to be at my top form and get ready for the grass to play at Wimbledon. I hope I can be ready to compete by then."

Wimbledon starts on June 22.

On Sunday, Nadal lost in the fourth round of the French Open to Sweden's Robin Soderling. It was the first loss at Roland Garros for the four-time French Open champion.

Nadal was also coming off a loss to Roger Federer in the final of the Madrid Open.

Nadal has played at the Queen's tournament in west London every year since his first appearance in 2005. He won the title last year, beating Novak Djokovic 7-6 (6), 7-5 in the final.

Kei Nishikori also withdrew Friday because of an elbow injury. No. 82-ranked Marco Baghdatis was given a wild card to replace him.