China's Zhang Shuai advanced to the second round of the Western & Southern Open after knocking out Russian Ekaterina Alexandrova 6-3, 6-4 in Cincinnati, Ohio, on Wednesday.
This is the first time that Zhang, who stunned Naomi Osaka in the first round, has reached the last 16 in Cincinnati, with her live ranking rising to 39th.
"I am happy to win today's match because my opponent was very strong and it was tough every time I played against her in the past," said Zhang, who lost to Alexandrova at April's Stuttgart Open.
"I'm satisfied with my performance today because I saw myself improve in many aspects," added the 33-year-old. Zhang will next face second-seeded Anett Kontaveit of Estonia, who defeated the Czech Republic's Tereza Martincova 3-6, 7-5, 6-4, on Tuesday.
Nadal beaten
Borna Coric spoiled the return of Rafael Nadal after a five-year absence from the Cincinnati Masters on Wednesday with a 7-6 (9),4-6, 6-3 upset victory in the second round.
The 36-year-old Spaniard, who won the Cincinnati title in 2013, was playing his first match in well over a month after an abdominal injury forced him to withdraw from his Wimbledon semifinal against Nick Kyrgios.
Nadal began the season with three titles and 20 consecutive wins but will head into the US Open after only one summer hard-court match.
"It was very, very special," Coric said. "I've been out the last two years injured. I didn't play on the big stage.
"I was looking forward to playing this match. It was all kind of crazy I would say."
Kyrgios, meanwhile, lost his way amid objections to on-court advertising lights, with the Wimbledon runner-up falling 6-3, 6-2 to American Taylor Fritz.
Women's 10th seed Emma Raducanu followed up her win over Serena Williams with victory over another major winner, Victoria Azarenka. The Briton crushed Azarenka 6-0, 6-2.
The teenage US Open champion claimed the first 10 games before Azarenka, a two-time Australian Open champion, finally captured a game.
Andy Murray needed a post-match on-court visit from the trainer after losing 3-6, 6-3, 6-4 to Cameron Norrie in the second round.
American Ben Shelton stunned fifth seed Casper Ruud, defeating the Norwegian 6-3, 6-3, while women's world No 1 Iga Swiatek beat Sloane Stephens 6-4, 7-5.