In-form teenager Mirra Andreeva went out of the Stuttgart Open as she lost in straight sets to fellow Russian Ekaterina Alexandrova in the last 16.
Sixth seed Andreeva, who has already won two titles this season, lost 6-3 6-2 against unseeded Alexandrova in just over an hour.
Andreeva, 17, became the youngest champion at a WTA 1000 event in February by winning the Dubai Tennis Championships, before triumphing at Indian Wells in March.
But she was unable to wrestle control of the match from Alexandrova, 30, who claimed her fourth win over a top-10 player this season.
Alexandrova will play American third seed Jessica Pegula in the quarter-finals after she thrashed Poland’s Magdalena Frech 6-1 6-1.
Italian fifth seed Jasmine Paolini beat unseeded German Jule Niemeier 6-1 7-5 to reach the last eight for the second successive year.
She will play the winner of Thursday’s match between American fourth seed Coco Gauff and Germany’s Ella Seidel.
Top seed Aryna Sabalenka will play Belgian Elise Mertens in the quarter-finals after Anastasia Potapova withdrew before their last-16 match with an injury.
The final last-eight tie sees Polish second seed Iga Swiatek take on either American seventh seed Emma Navarro or Latvia’s Jelena Ostapenko, with the pair set to play later on Thursday.
