Still, the top-seeded Sinner emerged to beat No.27 Denis Shapovalov 5-7 6-4 6-3 6-3 on Saturday to take his title defence at Flushing Meadows into the fourth round.
"Very tough match today. I know Denis a long time. The last time that we played was some years ago," Sinner said, referring to his defeat by the Canadian in the opening round of the 2021 Australian Open.
"We both have improved so much. I knew I had to play at a very high level. I'm happy that I managed to win. He started off very well.
"I tried to stay there mentally, trying to see what's coming. Thank you so much for the support. It's been amazing since so many years."
World No.1 Sinner stretched his hard-court grand slam winning streak to 24 matches, an unbeaten run that includes 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.
The 24-year-old Italian had won 14 sets in a row in New York since dropping one in a victory against 2021 champion Daniil Medvedev a year ago.
On Saturday, Sinner double-faulted to close the opener, 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, 0-30 in the third after Shapovalov - a left-hander who was a Wimbledon semi-finalist in 2021 - grabbed 14 of 17 points.
From there, Sinner took nine games in a row to seize control and set up a clash with Tommy Paul or Alexander Bublik in the fourth round.
"Week two is completely different," Sinner added.
"I'm looking forward to the next match. It's getting tougher physically and mentally, it's all different.
"It's a special place for me for many years. The first time that I played the main draw of a slam was here. And I won last year. It's an amazing place to be."
In a late match on Saturday, Felix Auger-Aliassime rallied from a set down to stun world No.3 Alexander Zverev 4-6 7-6 (9-7) 6-4 6-4 and reach the last 16.
Auger-Aliassime battled to pull off one of the biggest wins of his career, returning to the fourth round at Flushing Meadows for the first time since his 2021 semi-final run.
"I'm still young but it's been a few years and I'm working my way. Some of you might be the first time you're watching me tonight, but this feels really good," said the 25-year-old.
"The job's not done. Tournament is still going. But this means a lot to me. A lot of hard work. Many years of it."
The Canadian will face Russian Andrey Rublev in the next round.
with Reuters
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