Wimbledon is ready to kick into gear after a stop-start first week, with seven Grand Slam champions in action on 'Manic Monday' when all the men's and women's fourth-round matches are contested.

World number one Rafa Nadal has led the charge into the second week with his armour intact but the defending champion faces a potentially tricky encounter with 2009 US Open champion Juan Martin Del Potro.

The Argentine has been lurking in wait for the 10-times Grand Slam winner and his lowly 24th seeding belies ability that lifted him to number four in the world before a wrist injury forced him to miss most of last year.

"It is always a big challenge to play against him, he is a very tough opponent," Nadal told reporters after his third-round victory over Gilles Muller.

"He is one of the best players in the world but had an important injury last year."

Six-times winner Roger Federer, like Nadal, has eased through the first week without dropping a set while Novak Djokovic and Andy Murray ensured the top four seeds in the men's draw are still in place.

Federer plays Russian 18th seed Mikhail Youzhny while Djokovic takes on French serve and volleyer Michael Llodra.

Home favourite Andy Murray will be roared on by a partisan Centre Court crowd when he plays France's Richard Gasquet, whom he beat in five sets at the All England Club three years ago.

In the women's draw, Venus and Serena Williams have shaken off the rust from their time out of the game and look ominously poised to continue their stranglehold on the grasscourt Slam. They face Tsvetana Pironkova and Marion Bartoli respectively.

Russian Maria Sharapova, the 2004 champion who has roared herself into the fourth round with her decibel-busting grunts, plays China's Peng Shuai.