The Italian second seed led 6-2, 6-1 when France's Hugo Gaston called it quits with an apparent injury after 68 minutes on Rod Laver Arena.

Sinner faces Australian qualifier James Duckworth or Dino Prizmic of Croatia next.

"I saw that he was not serving at pace. It's not the way you want to win the match, but he's such a talented player," said Sinner.

"So I knew from the beginning that I had to play a very high level and was trying to be as aggressive as possible, which I've done.

"I'm very happy to be back here, it’s a very special place for me."

Sinner had made a sticky start, falling 40-0 down on his serve in the first game of the match, before rattling off three aces to hold.

It was about the only blip as the 24-year-old quickly found his devastating range to assert his authority over the 93rd-ranked Frenchman.

Sinner, who comfortably defeated Alexander Zverev in the final 12 months ago, raced to the first set in 37 minutes.

The 25-year-old Gaston had brief treatment between sets from the trainer and when they resumed Sinner tightened his grip on the contest.

Sinner romped through the second set and Gaston shook hands.

Should he win three titles in a row in Melbourne, Sinner would join Novak Djokovic as the only men in the Open era to do so.