Wildcard Jil Teichmann of Switzerland scored the biggest win of her career on Friday (IST) at the Western & Southern Open here, knocking out last year’s finalist and No.2 seed Naomi Osaka of Japan from a set down, 3-6, 6-3, 6-3.

Osaka was quick to take a 3-0 lead in the opener, but the Swiss used her natural athleticism and defensive skills to lure Osaka into long rallies, frustrating the four-time Grand Slam champion with her determination and variation of spin and slice.

Up next for Teichmann for a place in the biggest semifinal of her career will be her compatriot, No.10 seed Belinda Bencic, who advanced to the quarterfinals when Karolina Muchova of the Czech Republic retired due to injury trailing 7-5, 2-1.

Staring down a nearly identical deficit in the final set — serving at 2-0, 0-30 — Teichmann stopped Osaka’s momentum in its tracks, winning four straight games. Teichmann took a lead she’d never relinquish, despite double-faulting on break point when leading 4-2.

The loss is just Osaka’s fourth after winning the first set since 2017. It is also Teichmann’s third career top-10 win, first on hardcourt. Her prior wins over Dutch player Kiki Bertens, to win the title in Palermo in 2019, and Elina Svitolina of Ukraine, earlier this year in Madrid, came on clay.

The Swiss No.3 came into this tournament just 1-4 since suffering an ankle injury at the Internationaux de Strasbourg in May that forced her out of the French Open.

No.9 seed Barbora Krejcikova of the Czech Republic defeated No.8 seed Garbine Muguruza of Spain, 6-1, 6-7(5), 6-2 to reach the quarterfinals. The clash was a rematch of this season’s Dubai final, where 2017 Cincinnati champion Muguruza defeated Krejcikova, then ranked outside of the top-50, in straight sets.

However, Krejcikova’s surge to the top of the game has only accelerated since that week, and the newest member of the top-10 avenged that loss against the former world No.1 on the hardcourts of Cincinnati after 2 hours and 24 minutes of play.

Krejcikova will next have a quarterfinal meeting with world No.1 Ashleigh Barty of Australia, after the top seed cruised past defending champion Victoria Azarenka of Belarus 6-0, 6-2.

Germany’s Angelique Kerber overcame Jelena Ostapenko of Latvia 4-6, 6-2, 7-5. Kerber had lost a 4-6, 6-3, 6-4 thriller to Ostapenko in the third round of Rome in May, and a similar treat was promised to the Cincinnati fans when both players played their hearts out, racking up winner after winner in the opening stages.

Kerber will take on the winner of the clash between Czech Republic’s Petra Kvitova, whom she first played in 2007, and Ons Jabeur of Tunisia. Kerber has beaten both in their most recent meeting this year — Jabeur in the Grampians Trophy in Melbourne in January, and Kvitova in the Bad Homburg semifinals in June.