Facing Spanish qualifier Jaume Munar, the Serb delivered with a 7-6 (1), 6-4, 6-4 triumph to move into the third round for the 13th time.

Despite the victory, Djokovic found fault with his performance.

"I went through my ups and downs, and not really satisfied with my performance," Djokovic said after the match. "I just played enough in the right moments to win the match. So hopefully the level will increase and will get better in the next match."

Djokovic, who underwent right elbow surgery earlier this year, is the 20th-seeded player in Paris, his lowest Grand Slam seeding since the 2006 US Open. He arrived at Roland Garros with a 10-7 record this season.

He said he feels "comfortable" and his elbow isn't giving him problems thus far, but he knows he can play better.

"At the moment, I'm not playing at the level I wish to," Djokovic said. "But at the same time, I understand that it is the process that obviously takes time. And I'm trying to not give up and create the best out of this situation and circumstances that I'm in."

Djokovic hasn't won a Grand Slam title since claiming his fourth in a row at the 2016 French Open.

"At times, I do lose maybe a comfort level on the court and confidence, and that's something that I'm still building gradually, obviously," Djokovic said. "The more matches I play, the better it is. The more I win, of course, the better it is. Hopefully that can keep going."

Second-seeded Alexander Zverev trailed by a set and a break -- and was down a broken racket, too -- before eventually collecting himself and coming back to beat 60th-ranked Dusan Lajovic of Serbia 2-6, 7-5, 4-6, 6-1, 6-2.

"I mean, you guys make it sound like we think about it, really. We don't," Zverev said about trailing in a match. "We just try to play and win each point, each game. Being two sets to one down is like being a set [behind] in a three-set match.

"We're not going to overthink it: 'Oh, I'm two sets to one down. What am I going to do? How am I going to play the next point?' We try to play our best. We try to maybe change a few tactics and see how we can win the next point and the next game."

Zverev equaled his best showing at Roland Garros; he also reached the third round two years ago.

If the 21-year-old German is going to get to the round of 16 he'll need to do something he never has at a Grand Slam tournament: defeat a player ranked in the top 50. Zverev's next match comes against 26th-seeded Damir Dzumhur.

Lajovic lost his eighth consecutive match that stretched to five sets.

Fourth-seeded Grigor Dimitrov rallied to beat 21-year-old American Jared Donaldson 6-7 (2), 6-4, 4-6, 6-4, 10-8 in a marathon match that lasted 4 hours, 19 minutes on Court 18.

Donaldson could barely stand, let alone move well, as he started cramping late in the fifth set. He even tried an underhanded serve -- ala Michael Chang in 1989 -- but the unusual strategy didn't help.

When it ended, Dimitrov leaned forward while raising each knee to give it a kiss -- perhaps thanking his legs for carrying him to the win while Donaldson's gave way.

Donaldson, who is ranked 57th, was actually two points from winning when he led 6-5 in the fifth and got to love-30 on Dimitrov's serve. But Dimitrov took the next four points to hold for 6-all.

Dimitrov broke to lead 8-7 and served for the victory, but Donaldson broke right back.

In the next game, though, Donaldson started cramping. He double-faulted, and then he resorted to another underhand serve and lost the point. Dimitrov eventually got the break for a 9-8 edge as Donaldson slowly limped to the sideline for the changeover.

Another American,12th-seeded Sam Querrey, also bowed out early in his least successful Grand Slam tournament -- losing 1-6, 7-6 (3), 6-4, 6-1 by Gilles Simon of France.

Querrey hadn't even won a single match at Roland Garros since 2014 until beating Frances Tiafoe in the first round.

Querrey has been as far as the third round in Paris just once in 12 appearances.

Kei Nishikori rallied past local favorite Benoit Paire 6-3, 2-6, 4-6, 6-2, 6-3 to reach the third round in Paris for the fourth consecutive year.

"He was attacking every shot," Nishikori said of the nearly 3-hour match against the Frenchman. "He has one of the best touches on the Tour. It was fun to play him."

Jeremy Chardy first wasted a two-set lead and then bounced back to beat 17th-seeded Tomas Berdych 7-6 (5), 7-6 (8), 1-6, 5-7, 6-2.

Chardy led by two sets when their match was stopped by darkness on Tuesday, but Berdych mounted a comeback when they returned. Chardy played well in the decider and broke Berdych twice to advance.

"At two sets all, it was difficult in my head, and physically, too," said Chardy, who had never won in five previous matches against Berdych, who hadn't lost in the first round of any major since 2013. "I fought hard, all my body was shaking."

According to ESPN Stats & Information, Berdych fell to 0-40 in career matches after losing the first two sets -- the most losses without a win when trailing 2-0 by any player in the Open Era.