Polish world number two Iga Swiatek was knocked out of the Stuttgart Open quarterfinals by Jelena Ostapenko on Saturday, after third-ranked Jessica Pegula was eliminated earlier in the day.
Ostapenko, ranked 24 in the world, won 6-3, 3-6, 6-2.
Swiatek has now lost a remarkable six times to the Latvian in six attempts, with Saturday's loss the first on clay.
Swiatek, a two-time winner of the tournament, came into the match with an 11-1 record on the Stuttgart clay.
But Ostapenko won the first four games and broke Swiatek's serve three times to win the opening set.
Swiatek fought back to send the match to a final set, but Ostapenko regained control, winning 12 of the opening 15 points on the way to victory.
Ostapenko will face Russian Ekaterina Alexandrova in the semi-finals on Sunday, with the final on Monday.
Earlier on Saturday, Alexandrova continued her underdog run by dumping out Pegula in straight sets.
Alexandrova, who knocked out rising star Mirra Andreeva on Thursday in the last 16, beat the American 6-0, 6-4.
Pegula reached the final at the Miami Open in March and won the Charleston Open earlier in April but did not have an answer against her opponent, who is ranked 22nd in the world.
After failing to win a game in the first set, the 31-year-old American saved three match points at 5-2 down in the second. She fought off two more at 5-4 but could not hold on.
Alexandrova's five WTA top-10 wins are the equal most in 2025 with Andreeva and American Madison Keys.
Later on Saturday, world number one Aryna Sabalenka faces Elise Mertens. A beaten finalist three times in a row from 2021 to 2023, Sabalenka has never won in Stuttgart.
American world number four Coco Gauff will take on Italian Jasmine Paolini, who is ranked sixth in the world.