Cautious Rafael Nadal on guard as right knee worrisome

Rafael Nadal, the 2008 champion, is bracing for Monday's fourth round at Wimbledon, praying that his right knee can stand the strain of a run towards a dream second title.

His next test at the All England Club is a match with France's Paul-Henri Mathieu, nine times a victim of the world number one.

The second seed revealed after his weekend defeat of German Philipp Petzschner that he will be forced to skip champion Spain's Davis Cup quarter-final against France in a fortnight, instead undergoing a special treatment regime on his right knee.

The joint troubled him during Saturday's five-set win and Nadal said that the medical work is vital.

"I'm a little bit scared about the knee. I had this treatment (on his left knee) after Monte Carlo (and subsequently missed Barcelona the next week).       

"I didn't say anything at the time because when you lose it always looks like an excuse.

"It is a big disappointment not be in the Davis Cup on France. Playing in France for me is a very special confrontation and a very big motivation.       

"I talked with the captain, I talked with the president of the Federation a few days ago, and I said, 'Guys, I've never arrived at the US Open in one 100 percent condition.'

"I need to do this treatment after here. If I play Davis Cup, I don't have enough time to recover and play (hard court) tournaments. Everything was perfect for me last few months, and I need to be ready to finish the season well.

"My goal is try to keep having the chance to be number one for the rest of the season.  That's gonna be difficult. But if you are not in hundred percent of condition, it's going to be impossible."
       
While Nadal is feeling the pain after going five sets in two of his first three Wimbledon matches, the rest of the week two lineup is looking formidable.       

Top-seeded six-time champion Roger Federer has re-established his lethal rhythm in time to face Austrian Jurgen Melzer, a rare first meeting for both men at a Wimbledon edition where all six top seeds have reached the fourth round.

The level of competition so far has been particularly tough, with 28 five-set matches played through the 3rd round. The biggest five-set match count at Wimbledon since the 29 played in 1994 was highlighted by the 11:05 hour world record match between John Isner and Nicolas Mahut and their final set score of 70-68.

"There's always been big depth the last years," said Federer. "This year, there have been no major major upsets yet but tough matches for everyone.

"You always also have to respect the guy who put in a great effort and a good match. There's many guys that did that against top guys," said Federer.

Third-seeded Serb Novak Djokovic will go against 2002 champion Lleyton Hewitt while British fourth seed Andy Murray takes on American Sam Querrey.       

Andy Roddick, the fifth-seeded three-time finalist, plays the first Taiwanese player to get this far, Lu Yen-Hsun, while Swede Robin Soderling takes a perfect run so far - all wins in straight sets - into his contest with Spain's David Ferrer.

In the women's draw, the leading four seeds are still in the chase, paced by the one and two Williams sisters.

Serena Williams takes on Maria Sharapova in a re-run of the 2004 final won by the Russian while second seed Venus plays Australian Jarmila Groth.

Third seed Caroline Wozniacki faces Czech Petra Kvitova and number four Jelena Jankovic plays Vera Zvonareva and there is also the battle of Belgians Justine Henin and Kim Clijsters.