Juan Manuel Cerundolo of Argentina produced the biggest upset of the 2026 tennis season on 28 May, defeating World No. 1 Jannik Sinner in the second round of the French Open at Stade Roland Garros in Paris. The final scoreline — 3-6, 2-6, 7-5, 6-1, 6-1 — tells only part of the story of a physically gruelling contest that ended Sinner's bid to complete the Career Grand Slam.

How the Match Turned

Sinner appeared firmly in control, racing to a 5-1 lead in the third set, with a straightforward victory seemingly within reach. Then, visibly struggling with what appeared to be cramp, the Italian twice failed to serve out the match and was forced to take an off-court medical timeout at 5-4, 0/40.

From that point, the contest transformed entirely. Cerundolo, ranked World No. 56, seized the momentum and claimed an extraordinary 18 of the final 20 games to complete one of the most remarkable comebacks in recent Grand Slam history.

Historic Nature of the Upset

Cerundolo becomes the first man to eliminate the top seed at Roland Garros before the third round since Karol Kucera did so in 2000 — a span of 26 years. For the Argentine, it also marks his first-ever appearance in the third round of a Grand Slam tournament.

Sinner, who had swept all five ATP Masters 1000 titles in 2026 and carried a career-best 30-match winning streak into Paris, was chasing history. Roland Garros was the sole Grand Slam title missing from his collection, and victory would have made him just the seventh man in the Open Era to complete the Career Grand Slam.

What Cerundolo Said

'It's tough for him,' Cerundolo said of Sinner after the match. 'I couldn't win more than three games in a set, so I was a little bit lucky. He deserved to win this match, and then I don't know what happened. But I feel sorry for him and hope he recovers.'

The Argentine's candour underscored the unusual nature of the victory — one shaped as much by Sinner's physical deterioration as by Cerundolo's own quality, though his tactical exploitation of drop shots and wide angles once Sinner's movement was compromised was clinical.

Sinner's Season Context and Coaching Staff Response

Despite the physical distress, Sinner continued to produce flashes of brilliance — a series of thunderous planted forehands drew admiration even as his mobility waned. His coaching team, including Darren Cahill and Simone Vagnozzi, attempted to rally their player through the crisis, but the Paris heat and accumulated physical strain ultimately proved insurmountable.

Sinner departs the tournament with a 37-3 record in 2026, according to the Infosys ATP Win/Loss Index. His exit at Court Philippe-Chatrier follows last year's painful Roland Garros final, where he squandered three championship points against Carlos Alcaraz.

Wide-Open Draw After Sinner and Alcaraz Exits

The tournament landscape has shifted dramatically. Sinner and Alcaraz have shared the last nine Grand Slam titles between them, but with Sinner now eliminated and Alcaraz sidelined by a wrist injury, Roland Garros 2026 is set to produce its first new Grand Slam champion since the Australian Open 2024.

Cerundolo will next face either Spaniard Martin Landaluce or Czech player Vit Kopriva in the third round — uncharted territory for the Argentine, and a genuine opportunity to advance deep into a major for the first time.