World No. 2 Jannik Sinner extended his winning streak on indoor hard courts to 22 matches as he began his ATP Paris Masters campaign with a straight-sets victory over Zizou Bergs in the second round.

At the bottom of the draw, Sinner played just four days after lifting an ATP 500 crown in Vienna. The World No. 2 took the first set 6-4, displaying his usual mix of speed and touch.

Sinner has enjoyed another standout year, winning two Grand Slam titles for the second consecutive season. The 24-year-old also qualified for the ATP Finals in Turin for the third straight year and broke the Belgian to start the second set.

Carlos Alcaraz's unexpected defeat to Cameron Norrie opened the door for Sinner to potentially replace the Spaniard as World No. 1. If he wins the Paris title for the first time, he will return to the top spot just one week before the ATP Finals.

Sinner became the first man to reach eight tour-level finals in back-to-back seasons since Novak Djokovic in 2015-16. The second seed won the second set 6-2 and next faces Argentina's Francisco Cerundolo.

Germany's Daniel Altmaier upset Norway's World No. 9 Casper Ruud, who won his 14th title in Stockholm two weeks earlier. Altmaier took the first set 6-3 with rallies of impressive intensity.

Ruud, who had claimed his maiden Masters 1000 crown in Madrid in April, broke back for 5-all in the second set with a deep backhand.

Altmaier seeks a late-season surge on Europe's indoor hard courts to cap a career-best year, and the World No. 50 completed the upset by winning the second set 7-5. The German was set to face Canada's Felix Auger-Aliassime next.