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The pair were meeting for the fourth time since August, and eight days after their last clash, with the outcome the same as Sinner eased into the match before overpowering Auger-Aliassime, who needed medical attention during the second set.

Sinner extended his indoor hardcourt winning streak to 27 matches, his last defeat on the surface coming against Novak Djokovic in the 2023 ATP Finals decider.

The Italian is also in a battle with Carlos Alcaraz to end the year as world number one. Sinner must retain his title in Turin to have any chance, while the Spaniard can secure the prize by winning two more matches after victory in his opener.

Sinner began with intent by winning the first game to love and went on to give up just three points on serve in the opening set while forcing five break points, displaying an impressive mixture of sharp backhand and forehand shots down the line.

Auger-Aliassime hung in, smashing eight aces to Sinner's one during the first set, often at just the right time as he saved four break points, but the Italian came through when it mattered, breaking to win the set.

"It was a very tough match until 6-5. I had some chances to break," Sinner said.

"He played some very aggressive tennis, so I'm happy to overcome a very tough test today. Obviously winning the first match is very important in this competition and this format."

Sinner stormed into a 3-0 lead in the second and his opponent took a medical timeout for a problem in his left calf.

"I hope it's nothing too serious," Sinner said.

"I wish him obviously a very speedy recovery and hopefully he is back to 100 percent physically."

Auger-Aliassime saved two break points to avoid losing touch completely before Sinner sank the Canadian with another break to leave the Italian serving for the match, which he did in style, hammering home an ace to clinch the win.

While the Canadian struggled in the second set, Sinner began to enjoy himself, playing some deft drop shots to the delight of his home crowd, who rose to their feet to acclaim the win.

On Monday, German Alexander Zverev beat American Ben Shelton 6-3 7-6(6) in the other Bjorn Borg Group match. All four players in the group will meet each other with the top two qualifying for the semi-finals.

Tuesday's action features the Jimmy Connors Group, where Alcaraz takes on last year's finalist Taylor Fritz, with both players on one win each, and Italian Lorenzo Musetti faces Australian Alex de Minaur.