Karolina Pliskova, the second seed at Roland Garros, was knocked out of the French Open in the third round 6-3 6-3 by Croatia's Petra Martic.
Pliskova arrived in Paris after winning the biggest clay-court title of her career in Rome but it is not her best surface and the defeat was not a total shock given the calibre of her opponent.
Martic, who ranked 31 in the world, has had more clay-court wins than any other woman this season. She won a title in Istanbul and reached the semi-finals in Charleston.
She said: "I'm shaking right now, so many emotions in me. I can't think about numbers. It's time to play and I hope I'm going to continue this way."
The departure of Pliskova, plus Angelique Kerber's early exit, now opens up the bottom half of the draw and it's a half that includes the British No 1 Johanna Konta.
Konta will bid to reach the fourth round later on Friday when she faces Viktoria Kuzmova while Martic will meet an unseeded player in the last 16, either Estonia's Kaia Kanepi or Russian Veronika Kudermetova.
There was better news for Pliskova's fellow Czech Marketa Vondrousova as the 19-year-old reached the last 16 with a 6-4 6-4 defeat of Spanish 28th seed Carla Suarez Navarro.
Vondrousova will now face the 12th seed Anastasija Sevastova who emphatically saved five match points before converting one of her own to beat Elise Mertens 6-7 (7-3) 6-4 11-9 on Court Suzanne-Lenglen.
The clash took three hours and 18 minutes to complete as both players went toe-to-toe. The Latvian's progression into the fourth round marks her best result at Roland Garros.
Former champion Garbine Muguruza reached the fourth round for the sixth successive year with a 6-3 6-3 victory over ninth seed Elina Svitolina.
Muguruza, who won the title here in 2016, has a remarkable ability to find her best form at the Grand Slams and, after making the semi-finals last year, is again on a good run.
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