MELBOURNE, Australia >> When Carlos Alcaraz is on court for a training session, perhaps working on his newly revamped service motion, he’s doing so to buttress a game already good enough to claim four Grand Slam titles.

He’s also got his young rival, Jannik Sinner, in mind.

“The good thing for me is, when I’m seeing him winning titles, when I’m seeing him in the top of the ranking, it forces me to practice even harder every day,” Alcaraz said Saturday, a day before the start of the Australian Open.

Alcaraz, 21, and Sinner, 23, head into the 2025 tennis season at the top of the men’s game, coming off a year that portended greatness for both. With Rafael Nadal now joining Roger Federer in retirement, leaving 24-time major champion Novak Djokovic as the lone remaining member of the Big Three on tour, it appears as though Alcaraz and Sinner have separated themselves from the rest of the next generation, each taking two of the four Slam singles trophies in 2024.

Sinner is the defending champion in Australia, and went on to also win the U.S. Open in September, part of a season in which he went 73-6 with eight titles — but also dealt with a doping case in which he tested positive twice for trace amounts of an anabolic steroid.

Alcaraz exited from the Australian Open in the quarterfinals against Alexander Zverev last January, but then triumphed at the French Open, getting past Zverev in the final, and Wimbledon, where he won against Novak Djokovic in the final for the second year in a row.

On Sunday, Zverev faces wild-card entry Lucas Pouille at night.

Alcaraz, Sinner and Djokovic, along with five-time major champ Iga Swiatek and 2023 U.S. Open winner Coco Gauff, all will get started Monday.