Top-seeded Angelique Kerber of Germany received an opening-round test from Greece's Maria Sakkari before prevailing 6-4, 6-4 on Tuesday in the Hong Kong Open.
Sakkari won back-to-back games to pull within 5-4 in the second set before Kerber, the No. 1-ranked player in the world, closed out the match.
The German committed five double-faults in her victory.
Fifth-seeded Caroline Wozniacki continued her recent strong play by registering a 6-1, 6-4 victory over China's Zheng Saisai.
Wozniacki, from Denmark, rolled through the first set before being tested in the second.
Four-seeded Samantha Stosur of Australia was upset by Japan's Nao Hibinno 6-3, 6-4.
In other matches involving top-10 seeds, third-seeded Johanna Konta defeated fellow Englishwoman Naomi Broady 6-2, 6-2, sixth-seeded Caroline Garcia of France posted a 6-3, 6-0 victory over Tereza Martincova of the Czech Republic, and seventh-seeded Serbian Jelena Jankovic defeated American Samantha Crawford 6-3, 6-1.
American qualifier Shelby Rogers posted a 7-5, 4-6, 7-6 (4) victory over third-seeded Elena Vesnina in the opening round of the Tianjin Open in China.
Vesnina played a solid second set after losing the first. But the Russian wasn't able to maintain the same level of play in the third as Rogers prevailed in a tiebreaker.
American Alison Riske also pulled off an upset by notching a 2-6, 6-4, 6-3 win over fourth-seeded Timea Babos of Hungary.
Fifth-seeded Monica Puig of Puetro Rico also advanced with a 6-3, 7-6 (5) victory over Japan's Kurumi Nara.
Eighth-seeded Yaroslava Shvedova of Russia was ousted by Japan's Naomi Osaka, who won 6-4, 6-2.
Fourth-seeded Carla Suarez Navarro rolled to a 6-4, 6-2 victory over Germany's Mona Barthel in the opening round of the Generali Ladies Linz at Linz, Austria.
Suarez Navarro faces fellow Spaniard Sara Sorribes Tormo in the second round. Sorribes Tormo defeated Latvia's Jelena Ostapenko 7-6 (3), 6-4.
Denisa Allertova of the Czech Republic knocked off seventh-seeded Russian Daria Kasatkina 6-2, 6-3.