* Kostyuk claims 15th successive tour-level win on clay
* Unbeaten on clay in 2026 with titles in Rouen, Madrid
* Swiatek joins holder Gauff in exiting early in Paris
* Svitolina ensures Kostyuk showdown by beating Bencic
* Sabalenka favourite to win first Roland Garros crown
* Zverev, Jodar set up meeting with contrasting wins
By Shrivathsa Sridhar
PARIS, May 31 (Reuters) - Iga Swiatek's 25th birthday celebrations turned sour at the French Open on Sunday when the former champion lost to 15th seed Marta Kostyuk in the fourth round and her quest for a fifth title ended just when she had looked to be rediscovering her form.
Swiatek's shock 7-5 6-1 loss came amid a chaotic spell at Roland Garros, with men's world number one Jannik Sinner, 24-times Grand Slam winner Novak Djokovic and defending women's champion Coco Gauff all going out in the previous three days.
It leaves world number one Aryna Sabalenka as the favourite to lift her first title in Paris, though Ukrainian Kostyuk will be one to watch as she builds on the momentum that has helped her to sparkle on clay this season.
«I'm still in shock,» Kostyuk said in an on-court interview after reaching her first French Open quarter-final.
«I feel like I've given myself more space to just create something, to challenge my opponents. I woke up in the morning and all I thought was 'what an unbelievable day I have to live today... there's nothing I could do other than this'.
»I try not to focus at all on winning and losing, because I'm not playing tennis to win. I'm playing because I love it. I want to connect to people, feel this energy... make people happy and unite people.«
TOUGH DAY
It was a difficult day for Swiatek, who has forged her reputation as the »Queen of Clay« but has now gone two years without winning a title on the surface following her last triumph in Paris.
After her earliest defeat at Roland Garros since her debut campaign in 2019, Swiatek will now look to find comfort on grass ahead of her Wimbledon title defence starting on June 29.
»It wasn't a good day in the office,« said Swiatek, whose form has been patchy throughout the season.
»Many things I could manage a bit better, but it was super tough for me today to keep the level that I wanted to. Obviously at this stage any opponent in the fourth round who has already played couple of matches will use the opportunity.
«Congratulations to Marta.»
The French Open will crown new champions in both the men's and women's draws for the first time since Djokovic and Garbine Muguruza triumphed a decade ago.
One of the dark horses for the Musketeers' Cup will be teenager Rafael Jodar, who battled back from two sets down to beat veteran Pablo Carreno Busta 4-6 4-6 6-1 6-2 6-2 in their all-Spanish battle of the generations.
His next opponent, Alexander Zverev, is a more established contender with three trips to Grand Slam finals, and the German remained on track for an elusive maiden major by beating lucky loser and birthday boy Jesper De Jong 7-6(3) 6-4 6-1.
'ABSOLUTE JOY'
Romanian veteran Sorana Cirstea proved that dreams have no expiry date as she beat China's Wang Xinyu 6-3 7-6(4) to reach her first Roland Garros quarter-final in 17 years.
«I have so much passion for this sport,» said the 36-year-old Cirstea, who will retire at the end of the season.
«I absolutely love tennis and to be able to still play at this level, have my family, my team, the closest people watching me. It's an absolute joy.»
After a spell of rain cooled off Roland Garros, eighth seed Mirra Andreeva and Jil Teichmann began their match to decide who will meet Cirstea.
Kostyuk and Swiatek earlier sweated it out in the afternoon as they twice traded breaks, before the Ukrainian came up with a tight hold in the 11th game and raised her intensity to bag the first set with a backhand crosscourt winner.
It was the first time that Kostyuk had taken a set off the third-seeded Pole after three straight defeats in their previous meetings, and she sensed a big upset when she went ahead 3-1 in the next set after a battling effort.
The Rouen and Madrid champion held her nerve from there to take her record on clay this year to 15-0 on the tour, and book a meeting with seventh-seeded Ukrainian Elina Svitolina, who beat Swiss Belinda Bencic 4-6 6-4 6-0.
«She's paved the way for a lot of Ukrainian girls and boys, and she's doing great,» Kostyuk said about Svitolina.
«And especially this year, she's doing unbelievable. I'm so excited for this match. I've played with her two years ago, and I know a little bit what to expect.
»It's going to be a good match."
In other eagerly anticipated clashes, twice finalist Casper Ruud takes on Djokovic slayer Joao Fonseca in the evening while Jakub Mensik meets Andrey Rublev.
(Reporting by Shrivathsa Sridhar in Paris; Editing by Andrew Cawthorne, Ros Russell and Clare Fallon)
