Stan Wawrinka, the 2015 champion, is out of the French Open after a 2-6 6-3 6-3 4-6 6-0 loss to world number 239 Hugo Gaston in the third round.
The Swiss, who beat Andy Murray in the first round, was broken three times in the final set by the French wildcard, who was cheered to victory by the home support inside Suzanne Lenglen.
Gaston had not won an ATP Tour match before this year’s Roland Garros.
“It’s fantastic. It was a great match,” the 20-year-old said.
“I’m very happy today. Before I was always watching this on TV. Today I can play on these courts, so it’s amazing for me.”
Gaston, the lowest-ranked man to reach the fourth round at Roland Garros for 18 years, will now play US Open winner and third seed Dominic Thiem.
The 2018 and 2019 Roland Garros finalist booked his spot in the fourth round with a hard-fought 6-4 6-3 6-1 victory over Norwegian Casper Ruud.
The Austrian, 27, faced eight break points in the opening two sets, but was only broken once by the 28th seed, in the fourth game of the first set.
Thiem converted six of his chances as he gradually took control en route to victory in two hours and 15 minutes.
“Maybe the first four games were not as good as the rest of the match by me, but he’s a really good player,” said Thiem.
“He has a lot of confidence and has shown he is one of the best clay-court players this year. I tried not to give him chances in the third set.”
Meanwhile, sixth seed Alexander Zverev also progressed with a comfortable victory over Italy’s Marco Cecchinato.
The 23-year-old German, who lost in the US Open final last month, took one hour and 47 minutes to see off the world number 110 in a 6-1 7-5 6-3 win.
Zverev, looking to reach the quarter-final stage at Roland Garros for a third successive year, will face Jannik Sinner, after the promising 19-year-old Italian saw off Argentine Federico Coria 6-3 7-5 7-5.
We should start using Hawk-Eye on clay – Ruud
After his three-set win over Jack Sock on Wednesday, Thiem said there would be a point at Roland Garros where he would get “super tired” – during the early stages of his match against Ruud the new Grand Slam champion was certainly breathing hard.
Thiem saved break point in his opening service game before his resistance was finally broken in the fourth game. However, the steely Austrian broke back straight away with a ferocious forehand winner.
Thiem has one of the great defences in tennis and it was severely tested in a long sixth game, where he saved three break points. Rising star Ruud, 21, then dropped a level and was broken again as Thiem went on to take the opening set.
Ruud came to Paris in great form on clay, having reached the semi-finals in Rome and Hamburg. He went toe-to-toe with his opponent during the first two sets, and produced a ‘tweener’ lobbed winner, which brought applause from the sparse crowd under the roof inside Court Philippe Chatrier.
However, his defence was not as strong as Thiem’s and he was broken twice more in the second set before his challenge faded away in the third.
“I guess if we give him one more year, then he’s going to be super-dangerous,” said Thiem.
Ruud’s cause was also not helped by a couple of line calls not going in his favour, particularly one early in the second set which Thiem acknowledged was a “mistake” in his favour.
The Norwegian was insistent a return from Thiem had missed the baseline, only for the umpire to decide the ball had dropped in.
Most clay-court events, including the French Open, still have umpires going down on to the court to check ball marks, rather than relying on technology which is not yet deemed accurate enough on the surface.
Canada’s Denis Shapovalov was another player who fell the wrong side of a call on Thursday.
“I think definitely that we should start using Hawk-Eye for the clay-court tournaments as well because then we don’t need to have all these arguments with umpires,” said Ruud.
“And I think, quite frankly, we players are right on these mark discussions.”
Elsewhere, unseeded Italian Lorenzo Sonego won the longest men’s singles tie-break in Roland Garros history to oust American 27th seed Taylor Fritz 7-6 (7-5) 6-3 7-6 (19-17).
He will face Argentine 12th seed Diego Schwartzman, who won 7-6 (7-3) 6-3 6-3 against Slovakia’s Norbert Gombos.