World number one and champion Rafael Nadal's withdrawal from Wimbledon led to a major reshuffle in the men's draw on Friday. The Spaniard, who won the title for the first time last year after a mesmeric five-set final against Roger Federer, pulled out after deciding his painful knees could not survive two weeks of best-of-five-set matches. His spot on the top of the draw was taken by Argentine fifth seed Juan Martin del Potro, who had been in the lower half when the draw was initially made on Friday morning. Del Potro will open his campaign against the world number 49 Arnaud Clement of France and could face 2002 champion Lleyton Hewitt in the second round. Hewitt would probably welcome the switch since when he last met Nadal in a competitive match – in the third round of the French Open – he won only five games. French Open champion Federer, in pursuit of a record 15th grand slam title, will open his account against Taiwan's Lu Yen-hsun. However, he will have noted that he could run into Roland Garros runner-up Robin Soderling for the second time in less than a month in the last 16. Big-serving Croatian dangerman Ivo Karlovic lurks as a potential last-eight opponent. American sixth seed Andy Roddick, twice a runner-up in London, was paired with Frenchman Jeremy Chardy and could face del Potro in the quarter-finals. As a result of Nadal's absence, Germany's Nicolas Kiefer was promoted to 33rd seed and Brazilian lucky loser Thiago Alves was given a place in the 128-strong draw. There will be no top men's seed at Wimbledon this year. British world number three Andy Murray, hoping to become the first home winner of the men's title since Fred Perry in 1936, is now left as highest seed in the top half following Nadal's withdrawal and is slotted to meet Del Potro in the semis. He faces American Robert Kendrick in his opener. On paper it might appear to be a gentle start for Murray but Kendrick took Nadal to five sets in the second round in 2006 and the Briton is unlikely to underestimate the threat he poses. His quarter of the draw also includes 2008 semi-finalist Marat Safin, who is making his last appearance in London, and his conqueror at Roland Garros, Chile's Fernando Gonzalez. World number four Novak Djokovic will take on Frenchman Julien Benneteau and was drawn in the same half of the draw as Federer. Defending women's champion and third seed Venus Williams, who is the favourite to win a sixth singles title at the grasscourt championships, faces Swiss Stefanie Voegele and could line up against world number one Dinara Safina in the semis. There could be an all-Williams final showdown at Wimbledon for the second year running since the American sisters were picked in separate halves of the draw. Second seed Serena Williams, the US and Australian Opens holder, will begin against Portuguese qualifier Neuza Silva and could face a quarter-final showdown against 2004 champion Maria Sharapova. “I hope we can make the best out of this opportunity to meet each other in the final and hopefully we can make good of it,” Venus told Reuters. The top-half draw looks more treacherous for Venus since Serbs Jelena Jankovic and Ana Ivanovic and French Open champion Svetlana Kuznetsova all have the potential to trip her up if she has an off day. Kuznetsova will first face Japan's Akiko Morigami and could run into Safina in the last eight in a repeat of the Roland Garros final. Safina may, however, have to survive a fourth-round showdown with 2006 champion Amelie Mauresmo if she wants to earn a chance to gain revenge.