Elina Svitolina and Aryna Sabalenka eased into the Silicon Valley Classic quarterfinals on a good day for the seeds.
Svitolina, the top seed at the WTA Premier event in San Jose, was untroubled by Daria Kasatkina in a 6-3 6-1 victory on Wednesday.
The Ukrainian is enjoying another fine year and her last-eight clash with Maria Sakkari will mark her sixth quarterfinal of 2019 and she has won four of the previous five.
Sakkari, the seventh seed, was tested before getting past qualifier Mayo Hibi 4-6 6-4 6-2 at the hard-court tournament in California.
The second-seeded Sabalenka ended Coco Vandeweghe's first tournament of the year courtesy of a 6-3 6-3 victory.
Former world number nine Vandeweghe was making her return from ankle and foot injuries.
It was four from four for the seeds, with Carla Suarez Navarro beating Bethanie Mattek-Sands 3-6 6-1 6-2.
At the Citi Open, the only two seeds in action – Sofia Kenin and Monica Puig – departed.
Kenin went down to fellow American Lauren Davis 5-7 6-3 6-4 and Puig lost to qualifier Anna Kalinskaya 2-6 7-6 (7-5) 6-4.
Kristina Mladenovic edged 17-year-old wildcard Hailey Baptiste 6-4 4-6 6-3 and Jessica Pegula overcame Iga Swiatek 5-7 6-4 6-1.