Juan Martin del Potro has withdrawn from the Madrid Masters with a hip injury suffered in his opening-round match with Mikhail Youzhny. Del Potro defeated Marin Cilic on Wednesday and was scheduled to play Rafael Nadal in Thursday's night match. Nadal now advances to the quarterfinals, where he'll play either Michael Llodra or Daniel Gimeno-Traver. "I woke up very sore, " said Del Potro. "I tried to have a normal day, but I hurt more than I expected. The pain I have is very strong. Every day it gets worse. I did several tests and doctors saw something. I will follow what the doctors said: ‘do not play, if I do it is dangerous." —Ed McGrogan