WIMBLEDON, England - Rafael Nadal figured he couldn't win Wimbledon this year because of his achy knees, so he decided it didn't make sense to try.

Nadal withdrew from the grass-court Grand Slam tournament yesterday, 3 days before it begins, becoming only the second men's champion in 35 years to decline to defend his Wimbledon title.

"When I start a tournament like Wimbledon, it is to try to win," the No. 1-ranked Nadal said, "and my feeling right now is I'm not ready to play to win."

A subdued Nadal, wearing a purple T-shirt and white pants, spoke at a news conference yesterday evening at the All England Club, in the same room where he took questions after beating Roger Federer in the epic 2008 final that ended after 9 p.m. with light fading.

He announced his withdrawal about 2 1/2 hours after losing to 18th-ranked Stanislas Wawrinka in an exhibition match on grass at Hurlingham Club in South London.

"Today was the last test. I didn't feel terrible but not close to my best," said Nadal, who also lost an exhibition match against 2002 Wimbledon champion Lleyton Hewitt on Thursday. "I'm just not 100 percent. I'm better than I was a couple of weeks ago, but I just don't feel ready."

Nadal called it "one of the toughest decisions of my career," but he also added: "There's no option. I don't feel ready to compete 100 percent for 2 weeks."

He is the first reigning Wimbledon men's champion to pull out of the following year's tournament since Goran Ivanisevic in 2002.

By pulling out after yesterday morning's draw, Nadal forced organizers to shuffle the men's bracket. No. 5-seeded Juan Martin del Potro was moved from a potential semifinal against No. 2 Federer on the bottom half of the field into Nadal's old spot in the top half. And No. 17 James Blake switched from the top half to the bottom half in del Potro's old spot - and a possible semifinal against Federer. It also means that No. 6 Andy Roddick, a two-time Wimbledon runner-up, now could face del Potro - rather than Nadal - in the quarterfinals.

Meanwhile, on the women's side, the Williams sisters could be set for another Wimbledon final after they were placed in separate halves of the bracket.

Defending women's champion Venus Williams may have to overcome top-ranked Dinara Safina in the semifinals, while Serena could play fourth-ranked Elena Dementieva in the last four.

Safina was drawn against Lourdes Dominguez Lino, of Spain, in the first round. Venus Williams will take on Stefanie Voegele, of Switzerland, and Serena plays Neuza Silva of Portugal. *