The Italian star, widely tipped as one of the favourites for the title, appeared firmly in control of the contest after racing to a 6-3, 6-2, 5-1 lead and serving for the match in the third set. However, the encounter took a shocking turn as Sinner suddenly struggled physically, eventually collapsing to a five-set defeat.
The 22-year-old began showing visible signs of distress midway through the third set, losing 15 consecutive points before calling for a medical timeout. Courtside microphones captured him complaining of dizziness and nausea as Cerundolo mounted an unlikely comeback.
Despite receiving treatment on court, Sinner could not regain momentum. Cerundolo won six straight games to steal the third set 7-5 before taking control of the match completely. The Argentine broke Sinner twice in the fourth set and dominated the deciding set 6-1 to complete one of the tournament’s biggest upsets.
Throughout the latter stages of the match, Sinner repeatedly bent over in exhaustion and appeared unable to chase down balls effectively. He resorted to drop shots and serve-and-volley tactics in a desperate attempt to shorten rallies while also using ice packs and a handheld fan during changeovers to cool himself.
Temperatures reportedly rose from 29 degrees to 32 degrees during the match, though Sinner later insisted the weather was not the primary issue behind his collapse.
“I didn't feel very well on court,” Sinner said after the match. “I struggled, starting to feel very dizzy, very low on energy.
“I tried to serve it out but didn't have a lot of energy. In the fourth set, I let it go a little bit trying to have a bit more energy in the fifth. The first one was a very important game and I couldn't hold. Then it went a bit downwards.”
The Italian explained that he had already been feeling unwell before stepping onto the court.
“I woke up this morning, didn't feel very well and tried to keep the points very short. Also in the beginning I was hitting very clean, very good, and then I just kind of hit the wall, and that's it,” he said.
“The middle of the third set, even though I was playing some great tennis, but I really couldn't find any energy today.”
Sinner, who entered Roland-Garros on a remarkable 30-match winning streak dating back to February, admitted the defeat was difficult to process but remained optimistic about the season ahead.
“I always try to look at the positive side. If you watch the whole clay swing, [it has gone] very well. I played really good, winning three tournaments in a row on clay,” he stated.
“Coming here, also how I was playing tennis, I felt very well, hitting the ball in a good way, moving well and today was just not meant to be.”
The defeat also revived painful memories of last year’s French Open final, where Sinner squandered three match points against Carlos Alcaraz before losing in a dramatic fifth-set tiebreak.
Cerundolo, meanwhile, sympathised with his opponent while celebrating one of the biggest victories of his career.
“It's tough for him. He was winning the match. I couldn't win more than three games in any of the first two sets,” the Argentine said.
“I think I was a little bit lucky, I feel sorry for him. He was serving to win this match, but then I don't know what happened. I think he was cramping maybe, or maybe it was the pressure of the match.”
“But of course I feel sorry for him and I hope he recovers. I'm super happy. I'm going to keep trying to play my best.”
Elsewhere at Roland-Garros, French teenager Moise Kouame continued his fairytale run by reaching the third round after an exhausting five-set victory over Paraguay’s Adolfo Daniel Vallejo.
The 17-year-old wildcard triumphed 6-3, 7-5, 3-6, 2-6, 7-6 (10-8) in a marathon contest lasting nearly five hours, becoming the fifth-youngest player to reach the third round at the French Open since the Open Era began in 1968.
Fourth seed Felix Auger-Aliassime also progressed after recovering from a set down to defeat Roman Andres Burruchaga 4-6, 6-0, 7-5, 6-1. However, fifth seed Ben Shelton crashed out after a straight-sets defeat to Belgium’s Raphael Collignon.