(Reuters) - Ekaterina Alexandrova upset fellow Russian and No. 6 seed Mirra Andreeva 6-3, 6-2 in 65 minutes to reach the Porsche Tennis Grand Prix quarterfinals on Thursday in Stuttgart, Germany.
Alexandrova, 30, recorded her fourth Top 10 win of the season. She had 19 winners and eight aces while the 17-year-old Andreeva struggled with 24 unforced errors and landed only 48 percent of her first serves.
Top seed Aryna Sabalenka of Belarus won in a walkover due to an injury to Russia's Anastasia Potapova. Fourth-seeded Coco Gauff sailed past Germany's Ella Seidel 6-1, 6-1 in 57 minutes. American Jessica Pegula, the third seed, downed Poland's Magdalena Frech 6-1, 6-1 in 59 minutes, and fifth-seeded Jasmine Paolini of Italy defeated Germany's Jule Niemeier 6-1, 7-5 in one hour, 26 minutes.
In the final match of the day, Latvia's Jelena Ostapenko upset No. 7 seed Emma Navarro 7-5, 3-6, 6-2. Ostapenko converted 6 of 9 break points against her opponent while saving 14 of the 18 break points she faced.
Open Capfinances Rouen Metropole
Suzan Lamens of the Netherlands knocked off second-seeded Linda Noskova of the Czech Republic 6-4, 6-1 to qualify for the quarterfinals in Rouen, France.
Lamens saved 4 of 5 break points, while Noskova saved 6 of 11. Lamens won 81.8 percent of her first-serve points (27 of 33); Noskova was at 56.8 percent (25 of 44).
In other matches, top seed Elina Svitolina downed fellow Ukrainian Anhelina Kalinina 6-4, 6-0. Third-seeded Olga Danilovic of Serbia went three sets to defeat Czech Linda Fruhvirtova 6-2, 3-6, 6-4, and fifth-seeded Moyuka Uchijima of Japan rallied for a 1-6, 7-6 (4), 6-4 win over France's Lois Boisson.
The last match of the day saw Spaniard Jessica Bouzas Maneiro get past France's Varvara Gracheva 6-3, 6-3.