Canadian ninth seed Felix Auger-Aliassime came back from two sets down against qualifier Juan Pablo Varillas in his French Open first-round match.
The 21-year-old survived a huge scare on Philippe Chatrier after Peruvian world number 122 Varillas made a dream start on his Grand Slam debut.
Auger-Aliassime eventually prevailed 2-6 2-6 6-1 6-3 6-3 to end his wait for a main-draw victory at Roland Garros.
Alexander Zverev also progressed with a straight-set win over Sebastian Ofner.
The German third seed, 25, beat Austrian qualifier Ofner 6-2 6-4 6-4 and will play Serb Dusan Lajovic or Argentine Sebastian Baez in round two.
Having reached his first major quarter-final at Wimbledon last summer, Auger-Aliassime made the US Open semi-finals before a run to the last eight at the Australian Open in January.
But the Canadian was a clear second best early on against Varillas, 26, and appeared on course for a shock early exit in Paris as the Peruvian broke serve twice in both of the opening two sets.
A junior finalist at Roland Garros, Auger-Aliassime rallied in the third set as the momentum shifted emphatically in his favour, and he also dominated the fourth set to level the match.
In a much closer deciding set, it was the world number nine who was able to make the decisive breakthrough in the eighth game, serving out the match to complete a fine comeback and secure his first French Open main draw win at the third attempt.
"A first victory at Roland-Garros, but I had to work hard to obtain it," Auger-Aliassime said.
"It was a good opponent, who played a good match. I'm very satisfied with the way I finished. I needed a bit more space and a bit more time and I have a few tools in my game to help me get that."
Next for Auger-Aliassime will be either Russian Aslan Karatsev or qualifier Camilo Ugo Carabelli.
Elsewhere in the men's draw, 2018 and 2019 French Open runner-up Dominic Thiem lost an 11th successive match as the Austrian fell in straight sets to Bolivia's Hugo Dellien.
Argentine 15th seed Diego Schwartzman beat Russian Andrey Kuznetsov 6-3 1-6 6-4 6-2, while Bulgarian 18th seed Grigor Dimitrov prevailed 6-1 6-1 6-1 against American Marcos Giron.
American 23rd seed John Isner beat Frenchman Quentin Halys 7-6 (7-3) 4-6 7-6 (7-1) 7-6 (8-6), while Dutchman Botic van de Zandschulp, seeded 26th, won 6-3 3-6 6-3 6-2 against Russian Pavel Kotov.
Meanwhile, American 31st seed Jenson Brooksby was beaten 6-1 6-2 6-1 by Uruguayan Pablo Cuevas.
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