But an unforced error — a loose forehand long — let the Italian off.

Sinner followed up with a love hold, featuring one exquisite drop shot followed by a clinical lob.

After the defeat, Auger-Aliassime sat on his chair for a few moments with his head bowed.

"It was difficult having to sit there rethinking a few points, having to accept that the match is over," he said. "I wish I didn't make those mistakes to start the match with, I can't give him that at the level he plays."

Beating Sinner is a massive challenge indoors.

"There's no weather conditions that can impact the court, it's hard," Auger-Aliassime said. "He's so balanced and so well poised in his defense. On his return game, he's balanced everywhere."

He still has a chance of reaching Turin, and is vying with Italian Lorenzo Musetti for the coveted final spot. Both will be in action at ATP 250 tournaments, with Musetti playing in Athens and Auger-Aliassime the top seed in Metz, France.

Next up for Sinner?

"I will take a couple of days off. It's very important now for the body, but also for the mind," the 24-year-old said. "Recharge, and hopefully be as ready as possible for Turin."

Agencies via Xinhua