Japan’s Naomi Osaka hits a return to Katie Volynets of the US during their women’s singles match at the China Open tennis tournament in Beijing. AFP
Osaka defeated 60th-ranked American Katie Volynets 6-3, 6-2 and next faces Gauff in a showdown of former US Open champions in Beijing.
World number two Sabalenka swatted aside Ashlyn Krueger 6-2, 6-2 for her 14th victory in a row and plays another American in 24th-ranked Madison Keys.
Looking ahead to the Gauff meeting, four-time Grand Slam champion Osaka said: "She's very athletic obviously. For me, my strongest traits are being aggressive and also my serve.
"So it's definitely going to be a battle -- who wants to take control of the point first? And I think it's going to be me."
Former number one Osaka is playing her first tournament under Patrick Mouratoglou, the Frenchman best known for being the long-time former coach of Serena Williams.
The 26-year-old Japanese won four majors from 2018 to 2021 -- the US Open and Australian Open, both twice.
She is also a former winner in Beijing and has said she feels at home on the hard courts of the Chinese capital.
Osaka has struggled for consistency since returning to tennis in January after the birth of her daughter Shai and is ranked 73rd in the world.
Her best results after becoming a parent have been two quarter-final appearances.
The 2023 New York champion Gauff booked her place in the last 16 with a 7-5, 6-2 victory over Britain's Katie Boulter.
The 20-year-old American Gauff is seeded fourth.
She and Osaka have played four times previously, each winning twice. Their last meeting was in 2022 at San Jose when Gauff prevailed 6-4, 6-4.
Current US Open champion Sabalenka was error-prone in winning her opening match in Beijing against Thai qualifier Mananchaya Sawangkaew in straight sets.
But the Belarusian was on top form from the start against 68th-ranked Krueger.
The 26-year-old feels she is not quite playing the best tennis of her career, but said, "Control over my emotions, that's the key".
"Before it felt like if I'm not going to win this match, something bad is going to happen. I'm going to die," she explained.
"Nowadays I'm just working hard, I'm trying to improve myself every day. Every time I'm on the court, I'm trying to give my best. If you give your best but you didn't win the match, it's okay."
Sabalenka will take some stopping. Fourteen of her 16 titles have come on hard courts and only Iga Swiatek has won more matches on tour this season.
Top-ranked Swiatek is not in Beijing because of "personal matters".
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