The world number 76 produced a dogged display to defeat second seed and last year’s runner-up Osaka 3-6, 6-3, 6-3 to advance to the quarter-finals.

"I knew she's a very tough opponent," said Teichmann.

"She's a Grand Slam champion and I'm the underdog, so my plan was to just play my game.

"I move very good, I change up everything I can - directions, height, everything - and I think she didn't really feel very comfortable about it, and I served very good."

Teichmann moves through to face Belinda Bencic in an all-Swiss quarter-final.

The Swiss player, who claimed gold at the Tokyo 2020 Olympics earlier this month, led 7-5, 2-1 against Karolína Muchová before her Czech opponent retired due to injury.

Barbora Krejčíková, Petra Kvitová and Karolína Plíšková all progressed to ensure Czech Republic had three quarter-finalists in Cincinnati.

French Open champion Krejčíková claimed a 6-1, 6-7 (5-7), 6-2 victory over Spanish eighth seed Garbiñe Muguruza.

Kvitová was in scintillating form as she thumped Tunisia’s Ons Jabeur 6-1, 6-2, while Plíšková defeated Jessica Pegula of the United States 6-4, 7-6 (7-5).

Top seed Ashleigh Barty of Australia cruised into the last eight after thrashing Belarus’ 14th seed Victoria Azarenka 6-0, 6-2 and will now meet Krejčíková.

Former world number one Angelique Kerber of Germany came from behind to beat Latvia’s Jelena Ostapenko, while Spain’s Paula Badosa saw off Kazakhstan’s Elena Rybakina with a 6-2, 7-6 (7-5) triumph.

In the men’s event, Greece’s Stefanos Tsitsipas progressed to his fifth Association of Tennis Professionals Masters 1000 quarter-final of the season with a battling win over Lorenzo Sonego of Italy.

Sonego notched 15 winners to take the first set, only for the second seed to come storming back to complete a 5-7, 6-3, 6-4 triumph.

Tsitsipas will next face Canada’s Felix Auger-Aliassime, who upset Italy’s world number eight Matteo Berrettini with a 6-4, 6-3 victory.

"Today I played a great match," said Auger-Aliassime.

"At some points, he didn't play his best level but on the court, you have to deal with different situations and I was able to find my way through."

Top seed Daniil Medvedev of Russia overcame Bulgaria’s Grigor Dimitrov 6-3, 6-3 to extend his winning run to seven matches.

Fellow Russian Andrey Rublev battled hard to beat France’s Gael Monfils 7-6 (7-2), 7-6 (7-5).

He will now take on another Frenchman in Benoit Paire, who continued his brilliant run with a 7-6 (7-1), 6-7 (2-7), 6-1 success against John Isner of the US.

Olympic gold medallist Alexander Zverev of Germany dropped just four points on his first serve and did not face a break point as he defeated Argentina’s Guido Pella 6-2, 6-3.

Norway’s world number 11 Casper Rudd will hope to stop Zverev in his tracks after he booked his place in the last eight with a 6-4, 6-3 victory over Argentine Diego Schwartzman.

In the other last 16 clash, Spain’s Pablo Carreno Busta beat Poland’s Hubert Hurkacz 7-6 (8-6), 7-6 (7-3).