The world No. 1 exited Roland Garros in the second round after losing a five-set battle in brutal Paris conditions.

Jannik Sinner arrived at Roland Garros as the man to beat. He left it stunned, exhausted and beaten by an opponent more relentless than any player across the net: the heat.

The world No. 1 was eliminated in the second round of the French Open after a dramatic five-set defeat to Argentina’s Juan Manuel Cerúndolo, an unseeded player who seized the biggest victory of his career as Sinner’s body failed him in the punishing Paris conditions.

For two and a half sets, the match looked routine. Sinner controlled the tempo, struck cleanly from the baseline and appeared on course for another efficient victory. He won the first two sets 6-3, 6-2 and led 5-1 in the third, standing just one game from a place in the third round.

Then the match changed completely.

Sinner began to slow. His movement became heavier, his serve lost authority and his usually precise groundstrokes began to drift. The Italian called for medical attention as he battled visible physical discomfort, including dizziness and cramping. In the heat of Paris, the favorite suddenly looked vulnerable.

Cerúndolo, ranked outside the sport’s elite and carrying little of Sinner’s Grand Slam pedigree, did not retreat from the moment. The Argentine extended rallies, forced Sinner to move, and turned what had seemed like a lost match into a test of endurance. Point by point, the momentum shifted.

After saving himself from defeat in the third set, Cerúndolo surged. He took the set 7-5, then dominated the final two sets 6-1, 6-1 as Sinner faded physically and emotionally. What began as a routine victory for the top seed became one of the most shocking collapses of the tournament.

The defeat ended Sinner’s pursuit of a first French Open title and a career Grand Slam. It also transformed the men’s draw, removing the tournament favorite at an unexpectedly early stage. With Carlos Alcaraz absent through injury and Novak Djokovic no longer the overwhelming force he once was, Sinner had entered Paris as the clearest candidate to lift the trophy.

Instead, he was beaten by a combination of Cerúndolo’s resilience and the extreme physical demands of clay-court tennis in high temperatures.

The result also reopened questions about Sinner’s vulnerability in brutal conditions. His game is built on precision, rhythm and controlled aggression, but when heat and fatigue disrupt his timing, even his greatest strengths can begin to unravel. On this occasion, once his body began to fail, he could not recover.

Cerúndolo’s victory was the kind of career-defining upset that can reshape a player’s confidence. He did not simply benefit from Sinner’s physical struggles; he kept enough discipline and composure to force the champion-level opponent to play one more ball, one more game, one more set, until the match turned fully in his favor.

For Sinner, the loss will be difficult to process. He had led by two sets and was on the brink of victory, only to watch the match slip away in one of the most painful defeats of his career. The Italian is expected to shift his focus quickly toward recovery and the grass-court season, but the Roland Garros exit will linger.

The French Open has always been a tournament where champions must defeat more than opponents. They must master clay, pressure, long rallies, changing weather and the slow erosion of the body over five sets.

On Thursday in Paris, Jannik Sinner lost not only to Juan Manuel Cerúndolo, but to the conditions themselves.