Defending champion Stan Wawrinka recovered to beat Czech Lukas Rosol in the French Open first round.
Swiss Wawrinka, 31, who beat Novak Djokovic in last year’s final, eventually came through 4-6 6-1 3-6 6-3 6-4 in three hours and 11 minutes.
Spain’s Garbine Muguruza, last year’s Wimbledon finalist, progressed with a 3-6 6-3 6-3 win over Anna Karolina Schmiedlova of Slovakia.
Play was delayed by more than two hours because of rain at Roland Garros.
Tournament organisers were already facing a backlog of matches after only four hours of play were possible on Sunday because of rain.
British number one Andy Murray is scheduled to face 37-year-old Czech Radek Stepanek in the fourth match on Philippe-Chatrier Court.
Fellow Briton Kyle Edmund was due to start his campaign on Sunday but waited for the weather to improve before he faces qualifier Nikoloz Basilashvili, while compatriot Naomi Broady is scheduled to play American Coco Vandeweghe on court four.