Madrid - World number one Rafael Nadal advanced to the quarter-finals of the Madrid Open without hitting a ball on Thursday after his third-round opponent Philipp Kohlschreiber retired with a left foot injury.
Nadal, who is chasing a sixth title of the season and a fourth on clay, had been due to play the unseeded German later on Thursday. He will play either seventh seed Fernando Verdasco or wild card Juan Monaco in the last eight on Friday.
Nikolay Davydenko also pulled out of the tournament on Thursday because of a problem with his left leg, the ATP said.
The Russian 10th seed had been due to play Andy Roddick and the sixth-seeded American will take on world number two Roger Federer for a place in the last four.