Iga Swiatek's 25th birthday celebrations turned sour at the French Open on Sunday as the former champion lost 7-5 6-1 to Ukrainian 15th seed Marta Kostyuk, her bid for a fifth title ending just when she had looked to be rediscovering her rhythm.
There was little to separate the duo in the early exchanges as they twice traded breaks, before Kostyuk came up with a tight hold in the 11th game and raised her level at the end to claim the opening 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 season to 15-0, and book a meeting with seventh-seeded Ukrainian Elina Svitolina or 11th-seeded Swiss Belinda Bencic in the next round of Roland Garros.
"I'm still in shock," Kostyuk said in an on-court interview. "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 tennis because I love it. I want to connect to people, I want to feel this energy... make people happy and unite people."
Romanian veteran Sorana Cirstea beat China's Wang Xinyu 6-3 7-6(4) to advance to the quarter-final of a Grand Slam for just the third time in her career.
Cirstea is in the form of her life after becoming the oldest player to break into the top 20 earlier this month.
She reached two semi-finals during the claycourt swing and shocked world number one Aryna Sabalenka in Rome.
The Romanian also became the oldest player in the Open Era to claim a 6-0 6-0 win in a Grand Slam main draw with her third-round victory over Solana Sierra.
Against Wang, Cirstea dominated the opening set, breaking twice to surge into a 5-1 lead.
With the finish line in sight in the second set for Cirstea at 5-2, Wang fought back to force a tiebreak where the Romanian found a second wind to win in 84 minutes before the pair embraced at the net.
