Former champions Roger Federer and Serena Williams will look to continue their untroubled progress at the French Open on Sunday as they go hunting quarter-final places.
Federer, the 2009 winner, faces French 15th seed Gilles Simon, a player against whom he has a 3-2 record, including a victory on clay in Rome just two weeks ago.
A win for Federer will give him a 58th career victory Paris -- level with the record held by Guillermo Vilas and Nicola Pietrangeli.
The 17-time major winner has also been boosted by enjoying his best ever start to a French Open.
The 31-year-old has dropped just 23 games in three rounds compared to 24 in 2007 and 27 in 2010.
Although Simon has two wins against the great Swiss, the last of those came five years ago.
French sixth seed Jo-Wilfried Tsonga, his country's leading hope of ending France's 30-year wait for a men's champion, faces Serbia's Viktor Troicki.
Tommy Robredo takes on Spanish compatriot Nicolas Almagro for a place in the quarter-finals.
Robredo missed the 2011 and 2012 French Opens because of a leg injury which sent his world ranking plummeting to 471 just 12 months ago.
The former world number five was a quarter-finalist in 2003, 2005, 2007 and 2009.
Kevin Anderson, the first South African since Wayne Ferreira in 1996 to get this far, tackles Spanish fourth seed David Ferrer.
In the women's fourth round, world number one Williams, who is on a 27-match winning streak, faces Italy's Roberta Vinci.
Former champion Svetlana Kuznetsova faces German eighth seed Angelique Kerber.
Carla Suarez Navarro meets Sara Errani, last year's runner-up from Italy, while Polish fourth seed Agnieszka Radwanska plays another former champion Ana Ivanovic.