NEW YORK -- Jannik Sinner got broken for the first time in Week 1 of the US Open. Dropped the opening set, even. Fell way behind in the third set, too.
"I'm not a machine, you know," he said with the hint of a smile Saturday. "I also struggle, sometimes."
Still, Sinner is the No. 1-ranked player in men's tennis and has won the past three Grand Slam tournaments played on hard courts, so no one was surprised when he set aside some lapses and emerged to beat No. 27 Denis Shapovalov 5-7, 6-4, 6-3, 6-3 on Saturday to take his title defense at Flushing Meadows to the fourth round.
"That I have pressure and tension is normal. I've had that for a year, and you need to handle it," Sinner said. "Either you handle it -- or you don't. ... It's better to have to deal with that than not."
On Monday, Sinner will face No. 23 Alexander Bublik for a place in the quarterfinals. Bublik outlasted American Tommy Paul 7-6 (5), 6-7 (4), 6-3, 6-7 (5), 6-1 in their third-round match.
Sinner's latest triumph secured his 10th consecutive round of 16 major appearances and stretched his hard-court unbeaten run at Slams to 24 matches, covering championships at the US Open in 2024 and the Australian Open in 2024 and 2025. He also won the trophy at Wimbledon on grass courts in July.
But Sinner's set streak in New York ended; he had claimed 14 in a row since dropping one in a victory against 2021 champion Daniil Medvedev in the quarterfinals a year ago.
Sinner explained that his serve did not feel quite right Saturday, and that Shapovalov was reading it well.
"I was able to put pressure on Jannik today," Shapovalov said, "so who says that another player can't do the same?"
Sinner double-faulted to close the opening set, which earlier featured a remarkable 30-stroke point in which both men hit drop shots. Sinner took that point by sprinting back to the baseline and twisting his body to deliver a lob winner that floated just out of Shapovalov's reach.
After rebounding to even the match at a set apiece, Sinner found himself trailing 3-0, love-30 in the third after Shapovalov grabbed 14 of 17 points.
"Key moment," Sinner would say later.
From there, he took nine games in a row to seize control.
"We were going toe to toe. It was a very close match. A lot of games were very close," said Shapovalov, a left-hander from Canada who was a Wimbledon semifinalist in 2021. "He's No. 1 for a reason. He dealt with it really well. He fights extremely well. He did a tremendous job to turn it around down 3-0 in the third there."
With No. 7 seed Novak Djokovic and No. 2 Carlos Alcaraz both situated in the bottom half of the draw, Sinner does not have a major champion remaining in his half as he looks to become the first men's player to defend his title at Flushing Meadows since Roger Federer (2004 to 2008).
Earlier Saturday, world No. 435 Leandro Riedi of Switzerland became the lowest-ranked man to make the round of 16 at a major since No. 1,093 Richard Krajicek at 2002 Wimbledon, when Riedi's opponent Kamil Majchrzak retired after eight games due to injury.
Riedi is also the first man since Shapovalov in 2017 to reach the second week of the US Open after entering with zero major match wins.
Other men moving Saturday included Canada's Felix Auger-Aliassime, who knocked off third-seeded Alexander Zverev, Jaume Munar of Spain and No. 10 Lorenzo Musetti, whose opponent in an all-Italian match, No. 23 Flavio Cobolli, stopped because of right arm pain while trailing.
Also advancing via a retirement was Alex De Minaur, who led Daniel Altmaier 6-7 (7), 6-3, 6-4, 2-0 when the German stopped playing in the fourth set because of a thigh injury. De Minaur will be making his fifth career fourth-round appearance at the US Open, tying Rod Laver, John Newcombe and Ken Rosewall for the second-most such appearances by an Australian man since the Open era began in 1968. Only Lleyton Hewitt (8) has more.
No. 15 Andrey Rublev needed five sets but got past qualifier Coleman Wong 2-6, 6-4, 6-3, 4-6, 6-3.
ESPN Research and The Associated Press contributed to this report.