WUHAN – Poland's Maja Chwalinska claimed the highest-ranked scalp of her career Thursday, upsetting world No 11 Iva Jovic of the United States 6-4, 6-1 to reach the Wuhan Open quarterfinals, while Diana Shnaider knocked out sixth-seeded Karolina Muchova.

Chwalinska delivered a composed performance against Jovic, overcoming a series of demanding rallies to secure the biggest win of her career in terms of her opponent's ranking.

"I think it was quite a solid match from my side," Chwalinska said. "Iva is an amazing player. I knew that I needed to play my best game to get a win today."

The Pole said the contest had been tougher than the score suggested.

"We had many very challenging rallies and it was a very physical match, even though the score maybe doesn't show it," she said. "It was definitely a very hard match."

Chwalinska will next face Greece's Maria Sakkari, who defeated Slovak wild card Mia Pohankova 6-1, 6-4.

Shnaider also produced an upset, beating Muchova of the Czech Republic 7-5, 6-3 for her first victory in either singles or doubles at Wuhan in two years.

The result marked Shnaider's third win over a top-10 opponent this season.

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Fifth seed Elina Svitolina of Ukraine advanced with a 6-1, 6-4 victory over China's Guo Hanyu in one hour and 30 minutes, ending Guo's career-best run at a WTA 1000 tournament.

Guo praised Svitolina's ability to dictate play and vary her approach during rallies.

"What impressed me most today was how well she controlled the rhythm of the match," Guo said. "She knew when to take the risky, more aggressive option and when to play safer and more solid. That is the area I want to work on and improve in the future."

Despite her singles exit, Guo remains in the doubles competition alongside France's Kristina Mladenovic. The pair advanced to the quarterfinals following their opponents' withdrawal.

"We were a bit lucky," Guo said. "I can rest a little today and then prepare for the doubles match tomorrow."

Seventh-seeded Iga Swiatek of Poland eased past American Ashlyn Krueger 6-1, 6-4, while Ann Li of the United States defeated Indonesia's Janice Tjen 6-1, 7-6 (1).

Britain's Sonay Kartal recorded another notable upset, routing 15th-seeded Jasmine Paolini of Italy 6-2, 6-0.

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Latvia's Jelena Ostapenko also advanced after a three-set battle, defeating Canada's Leylah Fernandez 6-1, 1-6, 6-4.