World No 2 Aryna Sabalenka and fifth seed Coco Gauff both made surprise exits from German Open in Berlin on Thursday.
Belarusian Sabalenka, who was top seed at Steffi Graf Stadion, lost 6-2, 6-7 to Veronika Kudermetova, while American teenager Gauff was trounced 6-4, 6-0 by Ekaterina Alexandrova.
Wimbledon champion and second seed Elena Rybakina was beaten in three sets by Donna Vekic on Wednesday.
It was another disappointing defeat for Sabalenka – who lost to the unseeded Karolina Muchova in the French Open semi-finals earlier this month – with Wimbledon less than two weeks away.
Kudermetova, who beat Sabalenka at the same stage last year, outclassed her opponent in the first set, and was able to defend well against the serves, with her forehand particularly impressive.
Australian Open champion Sabalenka began to play some better tennis late in the second set after initially losing her serve and managed to force a tie-break, but failed to take Kudermetova into a third set.
“I’m super happy. For me it’s important to play like that. I know Aryna plays aggressive, I had to play aggressive too. I always believe in myself,” said the 26-year-old, who will now take on Alexandrova in the quarter-finals on Friday.
“I’m already a bit used to playing on grass, which maybe helped a bit.”
Meanwhile, Alexandrova extended her winning streak to seven matches, after defending her 's-Hertogenbosch title last week, with a 75-minute demolition of Gauff.
The 28-year-old had lost to Gauff in their only previous meeting at the 2021 Dubai Duty Free Tennis Championships but, after going 3-1 down in the first set, proceeded to win 11 of the last 12 games to seal her quarter-final spot.
“Grass is not my favourite surface, but somehow I'm managing to play so well on it,” admitted Alexandrova. “And maybe the score looks easy, but it's never like that because she played amazing.
“I needed to stay focused during every single point to keep it that way. I'm just hoping I can keep this form as long as I can.”
Jule Niemeier, who defeated defending champion and sixth seed Ons Jabeur in the first round, was forced to retire from her match against Marketa Vondrousova with the Czech 6-3, 6-5 ahead.
Vondrousova will now face the winner of sixth seed Maria Sakkari's match against Aliaksandra Sasnovich.
