PARIS — Like Novak Djokovic, Stan Wawrinka is a past French Open champion still working his way back into form after surgery.

Like Djokovic, Wawrinka is ranked lower than he has been in more than a decade. And like Djokovic, Wawrinka recently reunited with a coach who helped guide him to success earlier in his career.

Both men were in first-round action at Roland Garros on Monday, but unlike Djokovic, who won in straight sets, Wawrinka could not summon and sustain the sort of high-level play that has carried him to major titles in Paris and elsewhere. Returning to a place where he won the title in 2015 and made it back to the final a year ago, Wawrinka bowed out with a 6-2, 3-6, 4-6, 7-6 (5), 6-3 loss to 67th-ranked Guillermo Garcia-Lopez of Spain.

“I won three Grand Slams in my career, and I know what it takes to do it,” said Wawrinka, who was seeded 23rd and is ranked only 30th, territory unfamiliar to him since April 2008. “And my goal is to get to my top. Sooner or later, I will.”

Wawrinka only recently returned to the tour after missing three months to rest his left knee, which was operated on twice last August.

As Monday’s match stretched to 31/2 hours, Wawrinka was hindered by the physical strain of playing in a fifth set for the first time since his French Open semifinal victory over Andy Murray a year ago. But that wasn’t the biggest impediment to success.

“It was more the difficulty of continuing to go for it mentally,” he explained.

The owner of one of the prettiest one-handed backhands in the sport, Wawrinka only managed 12 winners, compared with 35 unforced errors, with that shot. He finished with 72 unforced errors in all.

“There is no frustration. It’s just tough,” said the 33-year-old Wawrinka.

Djokovic – a former No. 1 now ranked 22nd, his worst spot since 2006 – beat 134th-ranked qualifier Rogerio Dutra Silva of Brazil 6-3, 6-4, 6-4, quickly recovering after dropping the opening two games.

Since winning the 2016 French Open to complete a career Grand Slam, Djokovic has taken a step back. He has not added another major championship since, and after dealing with right elbow trouble for more than a year, he finally opted for surgery in February.

The third past men’s champion on the schedule for Day 2, No. 1-seeded Rafael Nadal, did not complete his match, which was suspended because of rain.

Beginning his bid for a record-extending 11th French Open title, he never quite seemed to be at his absolute best against 129th-ranked Simone Bolelli of Italy, and while Nadal grabbed the first two sets 6-4, 6-3, he was trailing 3-0 in the third when action was halted. They’ll resume Tuesday, when the most anticipated match of the tournament is scheduled for the main stadium: 23-time major champion Serena Williams, in her first Grand Slam match since January 2017, against 70th-ranked Kristyna Plyskova.