NEW YORK -- Top-seeded Jannik Sinner reached the US Open quarterfinals by shaking off a slow start and coming through in the clutch at the end of tiebreakers that decided the first two sets, then pulling away to get past No. 14 Tommy Paul 7-6 (3), 7-6 (5), 6-1 on Monday night.

Sinner -- two weeks removed from being cleared in a doping case stemming from two positive tests in March -- moved into a showdown against 2021 champion Daniil Medvedev, the last past winner at Flushing Meadows still in the men's field.

Sinner, a 23-year-old from Italy, claimed his first Grand Slam title at the Australian Open in January by defeating Medvedev in five sets in the final after dropping the first two. They also met in the Wimbledon quarterfinals in July, and Medvedev won that one.

Against Paul, Sinner was not at his best at the outset, falling behind by a double-break at 4-1 after 20 minutes at Arthur Ashe Stadium, where a loud crowd was backing the American, to no one's surprise.

As the match went on, plenty of chants of "U-S-A!" or "Let's go, Tommy! Let's go!" rang out. There also were several moments where spectators clapped after faults by Sinner - considered poor etiquette in tennis, that drew repeated admonishments from the chair umpire, who pleaded for no noise between first and second serves.

Sinner finished the initial set with 15 unforced errors on the forehand side alone, but he cleaned that up quickly and closed the match with just six the rest of the way.

"I can be very proud today, it was a tough opponent, so I'm very happy to be in the next round," said Sinner. "I didn't start very well (but) I tried to stay there mentally. And for sure, this today was one of the keys to win this match."

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

That meant Sinner has now won 14 of his past 15 tiebreakers, a stretch that dates to a tournament in Halle, Germany, in June. The lone exception was one he lost against Medvedev at Wimbledon.

Competing in New York a week after word emerged of his doping case - he tested positive twice for a trace amount of an anabolic steroid in March but avoided a suspension because it was ruled unintentional - Sinner dropped the first set he played at the U.S. Open. He's won the next 12.

Paul was trying to get his third career quarterfinal and first at Flushing Meadows. He also was trying to become the first American to beat a man ranked No. 1 at the US Open since Andre Agassi eliminated Lleyton Hewitt in 2002.

Instead, Paul fell to 0-6 at majors against players ranked in the top 10.

Sinner improved to 32-2 with four titles on hard courts in 2024 and he's now reached at least the quarterfinals at all four Slams this year.

Earlier Monday, the No. 5-seeded Medvedev picked up 6-0, 6-1, 6-3 victory over Nuno Borges that briefly was interrupted early in the third set when the electronic line-calling system was shut down because of a fire alarm.

The other quarterfinal on the top half of the men's bracket will be No. 10 Alex de Minaur vs. No. 25 Jack Draper. De Minaur beat Jordan Thompson 6-0, 3-6, 6-3, 7-5 in an all-Australian matchup, while Draper became the first British man in the U.S. Open quarterfinals since Andy Murray in 2016 by defeating Tomas Machac 6-3, 6-1, 6-2.

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

Information from The Associated and Reuters was used in this report.