World No. 1 Iga Swiatek survived in her return to hard courts at the Cincinnati Open, outlasting Varvara Gracheva 6-0, 6-7 (8), 6-2.

Playing for the first time since finishing third for Poland in the Paris Olympics, Swiatek set up a third-round match against Marta Kostyuk — a 6-3, 7-5 winner over Lulu Sun.

Swiatek won her third straight French Open title in May and has six WTA Tour victories this season.

Seventeen-year-old Mirra Andreeva beat 11th-seeded Emma Navarro 6-2, 6-2. Andreeva was playing her first match since taking a silver medal in doubles in Paris.

“I just went out there, tried to show my best level, and tried to win a match, and I think I did it,” Andreeva said.

Andreeva will face 2016 Cincinnati champion Karolina Pliskova.

Toronto semi-finalist Diana Shnaider of Russia, Andreeva’s doubles partner in Paris, beat Zhang Shuai 6-1, 6-4.

On the men’s side in the US Open tune-up event, world No. 1 Jannik Sinner got past American Alex Michelsen 6-4, 7-5 in his first match. Jiri Lehecka upset fourth-seeded Daniil Medvedev 7-6 (2), 6-4.

Sinner improved to 25-2 on hard courts this season and advanced to a third-round meeting with Australia’s Jordan Thompson. Sinner is trying to reach the quarterfinals in Cincinnati for the first time.

“I’m very happy to be in the next round,” the Italian star said. “For me this is a place where I used to struggle a lot in the past years, so let’s see what I can do this time.”

Thompson beat Sebastian Baez 6-2, 6-4.

Stefanos Tsitsipas, in his first tournament since announcing he would no longer be coached by his father, rallied to beat Jan-Lennard Struff 4-6, 6-4, 6-3.

Tsitsipas, the No. 9 seed, revealed that Apostolos Tsitsipas would no longer coach him after losing to Kei Nishikori in his first match last week in Montreal.