The Big Four of men's tennis push for quarter-final spots at the French Open on Monday, while Serena Williams and Maria Sharapova also feature in an action-packed Monday, thanks to Sunday's rain-hit schedule.
World number one Novak Djokovic, bidding for a first French Open to complete the career Grand Slam, faces French 20th seed Richard Gasquet. The top seed has a 10-1 winning record over Gasquet, whose only win over the Serb came eight years ago.
Djokovic will look to extend his run of successive Grand Slam quarter-finals to 24, while a win for Gasquet would make him just the third Frenchman to record 400 Tour-level match-wins. He is also looking for a place in the quarter-finals at Roland Garros for the first time in his 12th attempt.
Roger Federer, the second seed, returns to court after splitting the first two sets with Gael Monfils of France on Sunday before play was halted for bad light.
Andy Murray, the number three seed and twice a semi-finalist, faces unseeded Frenchman Jeremy Chardy defending a 6-1 career record, including a successful meeting on clay in Rome on the eve of Roland Garros.
Nine-time champion Rafael Nadal can clinch his 70th win at the French Open and reach a 10th quarter-final when he meets Jack Sock of the United States for the first time. Victory for 22-year-old Sock would make him the first American man to reach the Roland Garros quarter-finals since Andre Agassi in 2003.
In the women's fourth round, two-time champion and top seed Serena Williams resumes her sometimes testy relationship with American compatriot Sloane Stephens.
Defending champion Sharapova is first up on Court Philippe Chatrier against Czech left-hander Lucie Safarova in a match that was held over from Sunday.
French Open order of play on showcourts on Monday, the ninth day of the 2015 tournament at Roland Garros (x denotes seeded player; 0900 GMT start):
Court Philippe Chatrier
Lucie Safarova (CZE x13) v Maria Sharapova (RUS x2)
Gael Monfils (FRA x13) level with Roger Federer (SUI x2) To finish 3-6, 6-4
Serena Williams (USA x1) v Sloane Stephens (USA)
Novak Djokovic (SRB x1) v Richard Gasquet (FRA x20)
Court Suzanne Lenglen
Flavia Pennetta (ITA x28) v Garbine Muguruza (ESP x21)
Andy Murray (GBR x3) v Jeremy Chardy (FRA)
Jack Sock (USA) v Rafael Nadal (ESP x6)
Petra Kvitova (CZE x4) v Timea Bacsinszky (SUI x23)
Marin Cilic (CRO x9) v David Ferrer (ESP x7)
Sara Errani (ITA x17) v Julia Goerges (GER)
Andreea Mitu (ROM) v Alison Van Uytvanck (BEL)