Fourth seed Daniil Medvedev crashed out in the first round for the fourth year running, losing 6-4, 7-6 (7/3), 2-6, 6-1 to Hungary’s Marton Fucsovics.
The Russian, runner-up at last year’s US Open, became the highest-ranked player to fall so far and has yet to win a match at Roland Garros since his debut in 2017.
Italian journeyman Lorenzo Giustino carved out his own place in the headlines when he outlasted France’s Corentin Moutet 0-6, 7-6 (9/7), 7-6 (7/3), 2-6, 18-16 in the second longest match in French Open history at six hours and five minutes.
The match, held over from Sunday, fell 28 minutes short of Roland Garros’ record marathon tie between Fabrice Santoro and Arnaud Clement in 2004.
US Open winner Dominic Thiem, the runner-up to Nadal in Paris the past two years, defeated former Slam champion Marin Cilic 6-4, 6-3, 6-3.
“My level was good. I was very happy with the way I played from the beginning to the end basically,” said Thiem.
Having captured his maiden Slam in New York, Thiem is trying to become the only man in the Open era to win his first two majors at successive tournaments.
“I really love this tournament, it’s by far my best Grand Slam tournament so far,” said Thiem, who plays American qualifier Jack Sock in the second round.
“I’m from Austria so I know how it is to play in these cold conditions. I love it when it’s not too fast.”
Eighth seed Gael Monfils, the top Frenchman, lost 6-4, 7-5, 3-6, 6-3 to Alexander Bublik.
Play on Monday was initially delayed by more persistent rain. Petra Kvitova defeated Oceane Dodin 6-3, 7-5 in the only match to start on time under the new roof on Court Philippe Chatrier.
Kiki Bertens overhauled 112th-ranked Ukrainian Katarina Zavatska 2-6, 6-2, 6-0 once conditions improved while Elina Svitolina scrapped past Varvara Gracheva 7-6 (7/2), 6-4.
Garbine Muguruza, the 2016 champion, edged past Tamara Zidansek 7-5, 4-6, 8-6 but last year’s runner-up Marketa Vondrousova was bundled out 6-1, 6-2 by Polish teenager Iga Swiatek.