World number one Jannik Sinner suffered a shocking second-round exit at the French Open on Thursday, blowing a two-set lead to Argentina's Juan Manuel Cerundolo.

Top seed Sinner led 6-3, 6-2, and served twice for the match in the third set. The Italian appeared firmly in control at 5-4 in the third, but his level dropped sharply as temperatures climbed above 30 degrees Celsius, allowing the world No. 56 to take the remaining three sets 7-5, 6-1, 6-1.

"I didn't feel very well on court. I struggled, starting to feel very dizzy, very low on energy," Sinner said. "I was hitting very clean, very good, and then I just kind of hit the wall."

The four-time Grand Slam champion repeatedly bent over between points, used ice packs and a hand-held fan during changeovers, and later received medical treatment. Sinner admitted he had never felt so physically depleted during a match.

"I don't remember the last time I felt this weak," he said.

The defeat ended Sinner's 30-match winning streak dating back to March. Coming in as the overwhelming favorite after defending champion Carlos Alcaraz withdrew with a wrist injury, the 24-year-old had won five consecutive Masters 1000 titles, including Monte Carlo, Madrid and Rome. Earlier this month, he also became only the second player after Novak Djokovic to complete the set of all nine ATP Masters 1000 titles.

Cerundolo, meanwhile, produced the biggest win of his career to reach the third round. The Argentine said he sensed Sinner was struggling physically late in the match, but concentrated on extending rallies and staying patient. With Sinner out and Alcaraz absent, the men's draw has been thrown wide open.

China's Wu Yibing was also knocked out in the second round after losing 6-4, 6-4, 6-4 to Italy's 10th seed Flavio Cobolli in their second meeting of the season. Cobolli had also beaten him in the ATP 500 Acapulco quarterfinals.

"I've faced players with strong defense before, but today many of his returns were very deep, and even some of the high balls were difficult to handle," Wu said. "His serve and baseline game are also more suited to clay, and he controlled the rhythm of the match very well."

Wu was making only his second main-draw appearance at Roland Garros after first qualifying in 2023. Earlier this week, he defeated American Marcos Giron in straight sets to earn his first main-draw win at the French Open.

Elsewhere in the men's draw, Belgian Raphael Collignon upset fifth seed Ben Shelton 6-4, 7-5, 6-4. Nineteenth seed Frances Tiafoe survived a nearly five-hour battle against Hubert Hurkacz 6-7(5), 7-6(5), 6-4, 6-7(1), 6-4. Sixth seed Felix Auger-Aliassime also advanced after defeating Argentina's Roman Andres Burruchaga in four sets.