STUTTGART, Germany — One day after winning the Wimbledon title for the first time, Rafael Nadal pulled out of the Mercedes Cup on Monday with unspecified knee problems.

The second-ranked Spaniard traveled to the Weissenhof tennis center to tell promoters personally of his withdrawal as the clay-court event's defending champion and star attraction.

Doctors advised Nadal to take a few days off.

"I'm disappointed that I can't play," Nadal said.

Nadal dethroned Roger Federer as Wimbledon champion Sunday, needing 4 hours, 48 minutes to hold off the Swiss star's stirring comeback, 6-4, 6-4, 6-7 (5), 6-7 (8), 9-7.

The win was Nadal's first Grand Slam title outside the French Open, which he has won the last four years.