From typicallyspanish.com

Spain Sports News
Rafa Nadal withdraws from Stuttgart
By h.b.
Jul 8, 2008 - 7:49 AM

Rafa Nadal has announced in Stuttgart that he is retiring from the city’s tennis championship on medical advice from doctors who have ordered him to rest his knee.

Despite the decision the Spaniard, who won Wimbledon on Sunday, said it was the least he could do to travel to Germany to inform them personally about his withdrawal. He said that he had been playing for four or five months without pause, and now he has to rest.

Nadal is now 545 points behind Roger Federer in the world player rankings, and will lose 250 points by not defending his win last year in Germany. So far this year he has played 63 matches, with 56 wins and six titles.