Top seed Elina Svitolina of Ukraine and second seed Aryna Sabalenka of Belarus advanced to the quarter-finals of the WTA San Jose hardcourt tournament with straight-set victories Wednesday.
Svitolina defeated Russia's Darya Kasatkina 6-3, 6-1 while Sabalenka dispatched American Coco Vandeweghe 6-3, 6-3.
Seventh-ranked Svitolina booked a last-eight date against Greek seventh seed Maria Sakkari, who eliminated Japan's Mayo Hibi 4-6, 6-4, 6-2.
It was Svitolina's first match since Wimbledon, where she became the first woman from her homeland to reach a Grand Slam semifinal, and she improved to 5-0 against Kasatkina.
"I played quite a solid match for my first match on hardcourts," Svitolina said. "I'm excited for all the matches here and overall this part of the season."
Sabalenka, ranked 10th, advanced to a quarter-final against Spanish sixth seed Carla Suarez Navarro, who rallied past American Bethanie Mattek-Sands 3-6, 6-1, 6-2.
Mattek-Sands defeated fellow wildcard Venus Williams in the opening round.