Jannik Sinner will kick off his bid to defend his ATP Finals crown on Sunday, aiming to cap a turbulent year with another potential showdown against his great rival Carlos Alcaraz.

The world number one has already claimed two Grand Slam titles in 2025, including a landmark Wimbledon victory over Alcaraz, building on his triumph in Turin last year.

Both Sinner and Alcaraz are expected to advance from their respective Bjorn Borg and Jimmy Connors groups, setting the stage for a possible clash in the semifinals or final — a prospect that has fans eagerly anticipating another epic duel between the world’s top two players.

“If I manage to do it, great. If not, I’ve still had an incredible season — not with many tournaments, but with a lot of matches played and plenty of wins,” Sinner told reporters on Friday. “The first match is really important because usually you don’t play against one of the best eight players in the world, and that’s what makes it different.”

Sinner’s year has not been without controversy. A three-month ban interrupted his season after the World Anti-Doping Agency determined he was accidentally exposed to the banned substance clostebol last year. He also faced criticism for opting out of Italy’s Davis Cup title defense in Bologna. Some media outlets, skeptical of his South Tyrolean roots and Monaco residence, have even questioned his Italian identity — something Sinner has firmly rejected.

“I’m proud to be Italian,” he told Sky Italia in a wide-ranging interview earlier this week.

Despite these controversies, Sinner remains a fan favorite in Italy, and he will be cheered on by a strong home crowd in Turin, where he went unbeaten to claim last year’s title while Alcaraz failed to progress beyond the group stage.

A Friendly Rivalry

Although Sinner enters the tournament as world number one, he could still lose the year-end top spot depending on Alcaraz’s performance. The Spaniard is aiming for his first ATP Finals title and will look to add to his two Grand Slam victories this year, including a memorable Roland Garros final win over Sinner.

The two trained together on Friday, reflecting a rivalry built on respect rather than animosity.

“People might be surprised because when they think about our rivalry, they might think we hate each other,” Alcaraz said. “That’s not true. On court, we want to win. Off court, we are the same person. It’s a really healthy rivalry.”

Bigger Picture: Players Push for Change

The Finals come amid ongoing tensions between top players and the Grand Slam organizers over revenue sharing, player welfare, and consultation. This year, leading ATP and WTA players jointly demanded a greater share of tournament revenues and contributions to tour-funded programs such as pensions.

Women’s world number one Aryna Sabalenka expressed frustration this week over stalled discussions with the Slams, while the men, including Sinner and seventh seed Alex de Minaur, were more circumspect, despite participating in a player-representative meeting in Paris in May.

As the ATP Finals begin, Sinner’s focus is clear: navigate the group stage, defend his crown, and potentially renew one of tennis’ most compelling rivalries on the biggest stage.