For such a large proportion of Iga Świątek’s career, Court Philippe-Chatrier at Roland Garros has been her fortress. No matter the resume of the opponent before 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 – Swiatek seemed invincible on this court.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 a different dimension as the Pole put together the worst performance of her career in Paris. Her serve and confidence collapsing at once, Swiatek suffered 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 the first time Swiatek has lost before the semi-final stage since her debut fourth-round run in Paris.Her actual performance was even more unsatisfying. 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 lost 10 of the final 11 games.Across the net, her brilliant opponent had much to do with this result. This was always going to be a notable battle. After years of promise, dating back to her first breakthrough as a 15-year-old in 2018, the talented Kostyuk is finally putting things together. She is in by far the best form of her career and one of the most in-form players in the world, now on a career-best, 16-match winning streak after securing titles in Rouen and Madrid, her first WTA 1000. 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 that she belongs here. Most players step on to a clay court against Swiatek aware that only a spectacular performance would be enough to defeat her, but the amount of matches Kostyuk has won in recent months allowed her to understand during the match that being solid was what was most required of her here.Kostyuk possesses such a deep toolbox of shots, between her excellent athleticism, her variation and her ability to force herself inside the baseline in order to attack. In the past, the sheer number of options at her disposal made things even more complicated but she has gained clarity in her game. She used her tools well, soaking up pressure with her defence and remaining 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. With her back in the deep end of a grand slam tournament, performing at a high level and so full of confidence, it is clear Kostyuk can go even further.Yet the most notable aspect of this match was Swiatek’s dire performance. She had arrived in Paris in great spirits while seeking a fresh start to her career. A couple of months ago, a complete lack of confidence in her game had pushed her into splitting with Wim Fissette and hiring Francisco Roig as her new coach. She has thrown herself into this new partnership, completely buying into Roig’s philosophy. His proximity to her idol, Rafael Nadal, with whom he worked with for 18 years and who joined them on court during their first days together at the Rafa Nadal Academy in March, certainly helped.In their short time together, Swiatek has made major, long overdue technical changes to her first serve and their overall goal has been to restore the solid foundations of her game, to make her feel indestructible from the baseline in the key moments. The aspects of Swiatek’s game they have tried to improve – her serve and consistency – were far worse than before and cost her this match. Her inability to problem-solve, think clearly or fight back at all after the first set was alarming.With the honeymoon period in this 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. – Guardian