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Jannik Sinner, the world number two and two-time defending champion, commenced his title defense at the Australian Open with a commanding first-round victory over Hugo Gaston, who retired while trailing 6-2, 6-1. Despite this strong start, Sinner expressed concerns about his serve, which he has been adjusting since his loss to Carlos Alcaraz at the US Open. He leads the ATP Tour in service games won in 2025, achieving 92% success, yet he feels there is still room for improvement, particularly in the rhythm and reliability of his serve. Sinner's next match will be against Australian wildcard James Duckworth. Other notable results from the first round included Lorenzo Musetti advancing after Raphael Collignon retired, and veteran Gael Monfils facing defeat in what is expected to be his final Australian Open appearance. Several other seeded players also advanced, while some experienced early exits due to injuries.