Juan Martin del Potro has hip injury

MADRID -- Juan Martin del Potro withdrew from the Madrid Open on Thursday with an injury that could force him to miss the French Open.

The former U.S. Open champion said a pain in his left hip forced him to pull out of Thursday's third-round match with top-ranked Rafael Nadal.

"The pain is getting worse day by day so I didn't want to risk it," Del Potro said. "I have experience about injuries so I took the decision not to play."

Del Potro first felt the pain when he won the Estoril Open on Sunday.

"Hopefully I can recover quickly and it's nothing serious," said Del Potro, who beat Marin Cilic in straight sets Wednesday. "I won't be in Rome and I don't know if I'll be able to play in Nice or Roland Garros."

Del Potro, who called the pain "strong," said he would travel back to Argentina to treat the problem, ruling him out of next week's Rome Masters.

The 32nd-ranked Argentine had begun to find his form after missing most of 2010 following wrist surgery. The 22-year-old was ranked No. 481 on Jan. 31, but wins at Delray Beach and Estoril seemed to put him in contention for the upcoming Grand Slams.

"It's not nice to have to withdraw from this tournament and this game, which would have been nice to play, but I'm not in shape," Del Potro said. "I tried, but I'm not in shape to play."