Jiri Lehecka, two matches into his return from a back injury, is already showing top form.

The Czech player upset fourth-seeded Daniil Medvedev of Russia 7-6 (2), 6-4 on Wednesday to reach the third round at the Cincinnati Open in Mason, Ohio.

Lehecka had been out for three months due to a back injury before getting back on the court this week.

His next opponent will be the United States’ Frances Tiafoe, who downed 14th-seeded Lorenzo Musetti of Italy 6-3, 6-2.

No. 1 seed Jannik Sinner of Italy swept American qualifier Alex Michelsen 6-4, 7-5 in a second-round match. Sinner saved 8 of 8 break points and had sizable advantages in aces (9-1) and winners (28-14).

“It was a tough match. He played already … but for me it was the first match here, so I tried to feel the conditions a bit more,” said Sinner, who had a first-round bye. “I’m very happy to be in the next round. 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.”

Next up for Sinner is a match against Australia’s Jordan Thompson, who thrashed Argentina’s Sebastian Baez 6-2, 6-4.

No. 9 seed Stefanos Tsitsipas of Greece and No. 15 seed Holger Rune of Denmark both had to rally to ward off first-round upsets.

Tsitsipas came away with a 4-6, 6-4, 6-3 victory over Germany’s Jan-Lennard Struff, while Rune beat Italian wild card Matteo Berrettini 2-6, 6-1, 6-4.

Thanks in large part to six aces in the second set and eight in the third, Tsitsipas finished with 18 in the match. Struff totaled nine.

“I felt like I was in a great flow state towards the end of the match with my serve,” Tsitsipas said. “Immediately my groundstrokes improved, immediately my confidence to come forward and close in improved, so there were a lot of improvements that contributed to my game.”

Great Britain’s Jack Draper will be Tsitsipas’ next opponent after downing Spanish qualifier Jaume Munar 7-5, 3-6, 7-6 (5) on Wednesday.

Meanwhile, Rune collected 20 winners to record his first-ever win at the Cincinnati Open, a tournament that he is playing in for the third time. Berrettini saw a 10-match winning streak come to an end.

Rune is off to play Portuguese qualifier Nuno Borges, a 6-4, 3-6, 6-1 winner over Frenchman Adrian Mannarino.

The United States’ Sebastian Korda, the 16th seed, dropped his opening-round match 7-5, 6-1 to Pablo Carreno Busta of Spain, who is playing on a protected ranking.

Other first-round winners Wednesday included Canada’s Felix Auger-Aliassime, Hungarian Fabian Marozsan, Gael Monfils of France, Argentina’s Tomas Martin Etcheverry and Australian wild card Max Purcell.

–Field Level Media