NEW YORK — Top-seeded Jannik Sinner advanced to the quarterfinals of the US Open by shaking off a slow start and making a decisive breakthrough at the end of the tiebreakers that decided the first two sets. He then defeated No. 14 Tommy Paul 7-6 (3), 7-6 (5), 6-1 on Monday night.

Two weeks after being acquitted in a doping case stemming from two positive tests in March, Sinner faced 2021 champion Daniil Medvedev, the only former winner at Flushing Meadows remaining in the men’s field.

Sinner, a 23-year-old from Italy, won his first Grand Slam title at the Australian Open in January, beating Medvedev in five sets in the final after losing the first two. They also met in the quarterfinals of Wimbledon in July, with Medvedev winning that.

“I’ll have to do a lot of running,” Sinner said, “so hopefully I’ll be physically ready.”

Sinner initially did not play at his best against Paul. After 20 minutes in the Arthur Ashe Stadium he was facing a 4-1 deficit.

“That’s where you want to be. … It’s definitely different than any other setting,” Paul said. “It’s electric.”

A noisy crowd supported the American, which came as no surprise to anyone.

As the match progressed, there were many chants of “USA!” or “Let’s go, Tommy! Let’s go!” There were also several moments when spectators clapped after mistakes by Sinner – considered bad etiquette in tennis, which earned repeated admonitions from the chair umpire, who begged for no noise between the first and second serves.

Sinner closed the first set with 15 unforced errors on the forehand side alone, but he quickly corrected them and the match ended with just six errors.

“A tough match,” Sinner said. “Of course I believe that sometimes I can play a few points better … But he is a tough opponent. You have to accept that he moves very well, he can shake up the game. So I am happy with the win.”

Everything depended on the tiebreakers. The first was 3-all before Sinner took the last four points. Paul led 5-4 in the second, but Sinner took the last three points.

That means Sinner has now won 14 of his last 15 tiebreakers, a streak that dates back to a tournament in Halle, Germany, in June. The only exception was one he lost to Medvedev at Wimbledon.

Sinner lost the first set he played at the US Open, but won the next 12 sets.

Paul was attempting to reach his third career quarterfinal, his first at Flushing Meadows. He was also attempting to become the first American to defeat a man ranked No. 1 at the U.S. Open since Andre Agassi knocked out Lleyton Hewitt in 2002.

Instead, Paul lost his majors record 0-6 against top 10 players.

“I had chances there in the first set, obviously, and then chances in the second,” Paul said. “But he stepped up on the big points, and I didn’t. That was kind of the story of the match.”

Sinner improved his record to 32-2 with four hardcourt titles in 2024 and has now reached at least the quarterfinals at all four Grand Slams this year.

Earlier on Monday, the fifth-seeded Medvedev secured a 6-0, 6-1, 6-3 victory over Nuno Borges. The win was briefly interrupted early in the third set when the electronic system for calling the players’ line was disabled due to a fire alarm.

The other quarterfinal in the top half of the men’s pool is No. 10 Alex de Minaur vs. No. 25 Jack Draper. De Minaur defeated Jordan Thompson 6-0, 3-6, 6-3, 7-5 in an all-Australian matchup, while Draper became the first British man in the US Open quarterfinals since Andy Murray in 2016 by beating Tomas Machac 6-3, 6-1, 6-2.

The men’s quarterfinals on Tuesday are No. 4 Alexander Zverev vs. No. 12 Taylor Fritz, and No. 9 Grigor Dimitrov vs. No. 20 Frances Tiafoe.

This report used information from Coley Harvey of ESPN and The Associated Press.