For such a large proportion of Iga Swiatek’s career, Court Philippe-Chatrier at Roland Garros has been her fortress. No matter the résumé of the opponent in front of her, the significance of the occasion or even how badly she might have been feeling on court, she always found a way through. By the time she won her fourth French Open title in five years – her third in succession – the Pole seemed invincible here.

It has been only two years since the six-time grand slam champion last tasted success in Paris, yet on a mercifully cool Sunday afternoon, it felt as if that version of Swiatek was from an alternate universe as she put together the most difficult performance of her career in Paris. She endured a miserable 7-5, 6-1 defeat on her 25th birthday to the 15th seed, Marta Kostyuk, ending her run in the fourth round.

Even last year, when Swiatek was struggling to rediscover her joy on court in the aftermath of her positive doping test, which she successfully proved was the consequence of her taking a contaminated batch of melatonin, things were never this bad. This is her earliest exit since her debut fourth-round run in Paris in 2019.

Her actual performance was even more concerning. Swiatek’s serve completely collapsed midway through the match, with the third seed losing six consecutive service games to end the match, and she offered minimal fight once the wheels fell off. From 5-4, 15-15 in set one, Swiatek also lost 10 of the final 11 games.

Afterwards, she calmly explained why she was simply far too tense to play her tennis. “It is harder a bit to handle stress for me in last year, especially I feel like the peak was in the US this year,” she said. “So I feel like today I felt off, you know, and I did mistakes that I didn’t want to do, and I wanted to play safe, but the ball flew everywhere. Suddenly these feelings came back, and I tried to work on it with my dialogue inside, but it was tough today.”

Across the net, her supremely confident opponent had much to do with this result. After years of promise, dating back to her breakthrough as a 15-year-old, the talented Kostyuk is finally putting things together. She is in by far the best form of her career and on a 16-match winning streak after securing titles in Rouen and Madrid, her first WTA 1000 title. This is the second grand slam quarter-final of the Ukrainian’s career after first doing so at the 2024 Australian Open.

In their four previous meetings, Kostyuk had never even sniffed a set, but the 23-year-old entered this match full of belief. She possesses such a deep toolbox of shots, between her excellent athleticism and variation. She soaked up pressure with her defence and remained solid from the baseline while choosing her moments smartly to force herself inside the baseline, particularly with the sustained pressure she imposed on Swiatek’s second serve.

At no point did Kostyuk give Swiatek reason to believe that she might falter, and she never did. “I think I just give myself more space,” she said. “I’m enjoying more, just creating points, dealing with challenges, learning how to navigate the difficult situations in the matches. I have been doing it well, so happy with that.”

Still, the most notable aspect of this match was Swiatek’s level. She had arrived in Paris in great spirits while seeking a fresh start to her career with her new coach Francisco Roig. In their short time together, Swiatek has made major technical changes to her first serve and their overall goal has been to restore the solid foundations of her game, which were missing on Sunday.

“I think the serve is the most complicated shot,” said Swiatek. “So if something will fall apart a bit under pressure, I feel like it’s serve and then movement and then just mis-hitting everything. So I guess that happened today.”

With the honeymoon period of their partnership now over, Swiatek, Roig and the rest of her team will have much to think about as they try to ensure that the most successful player of this generation returns to competing at a level worthy of her ability. As for Kostyuk, an all-Ukrainian quarter-final between two of the most in-form players awaits as she next faces the seventh seed, Elina Svitolina. The Italian Open champion defeated Belinda Bencic, the 11th seed, 4-6, 6-4, 6-0.

Meanwhile, Sorana Cirstea continues to put together the best season of her life in her final year on tour. The 18th seed returned to the quarter-finals of the French Open for the first time since her breakthrough run in 2009 with a 6-3, 7-6 (4) win over Wang Xinyu of China.

On Monday, the battle between the top seed, Aryna Sabalenka, and Naomi Osaka, both four-time grand slam champions, will be the first women’s match to command the night session at Roland Garros since 2023.