Jannik Sinner began his Australian Open title defense with a straightforward win after Hugo Gaston retired at 6-2, 6-1. The world number two admitted he doesn't yet "feel very safe" with his serve despite making changes since his US Open loss. He held a 92% service game win rate in 2025.

Sinner, a two-time defending champion, dominated except for an early 0-40 deficit he saved. He served six aces and broke Gaston four times consecutively. The Italian has adjusted his serve rhythm, slowing the start, but still seeks consistency on this crucial shot as he eyes another deep Melbourne run.

Elsewhere, Gael Monfils played his final Australian Open, losing in four sets to Dane Sweeny. The 39-year-old Frenchman, retiring at season's end, thanked the Melbourne crowd. Other seeds like Ben Shelton and Taylor Fritz advanced, while Grigor Dimitrov suffered an early exit.