On Thursday, 16th seeded Caroline Wozniacki overcame several scares to edge past Czech No. 47 Katerina Siniakova in straight sets 7-5, 6-4, reports Xinhua news agency.
Up next for Wozniacki is Daria Kasatkina, after the Russian defeated her compatriot Ekaterina Alexandrova 6-4, 6-3, despite making no fewer than nine double faults over the course of the match.
World No. 4 Naomi Osaka of Japan logged another straight-set win, moving past Wuhan Open runner-up Alison Riske 6-4, 6-0.
The Japanese now faces a quarterfinal against US Open champion Bianca Andreescu, after the Canadian made short work of qualifier Jennifer Brady, defeating the American 6-1, 6-3.
In the men's draw, world number 19 John Isner fired off 21 on his way to a hard-fought 7-6 (3), 7-5 win over British qualifier Daniel Evans in just under two hours.
Isner faces 3rd seed Stefanos Tsitsipas in the quarterfinals, who stunned defending China Open singles champion Nikoloz Basilashvili 4-6, 6-3, 6-2 in a three-set marathon.
The last men's match of the day saw No. 2 seed Alexander Zverev issue a real statement of intent, dispatching Felix Auger-Aliassime of Canada 6-3, 6-1 in impressively quick fashion.
The German will face Sam Querrey, after the American served up 32 aces on his way to defeating Argentina's Diego Schwartzman 7-6 (2), 6-7 (6), 6-3.