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The 2025 season has been defined by the extraordinary dominance of Carlos Alcaraz and Jannik Sinner. The two have continued their modern-era duopoly, splitting all four Grand Slam titles between them for the second consecutive year. Their reign has been so remarkable that former legends like Roger Federer, along with current top-five players such as Alexander Zverev, have publicly voiced concerns over what they perceive as preferential treatment through court-speed homogenization.

Yet, despite the criticism, Alcaraz and Sinner, or “SinCaraz,” as fans have dubbed them, have remained unshaken, winning on every surface and in every condition. In fact, every tournament in 2025 that featured both players in the draw was won by either one of them.

Their dominance has created a massive points gap in the ATP rankings; both men sit above 10,000 points, while the third-ranked player trails below 5,000. Heading into the season’s final event in Turin, both still have a mathematical chance to end the year as the world No.1.

How the Year-End No.1 Race Stands

Sinner began 2025 as the world No.1 and held the top spot until the US Open, where Alcaraz defeated him in the final to reclaim No.1 for the first time in over two years. However, Sinner’s recent victory at the Rolex Paris Masters has once again shifted the rankings, propelling the Italian back to the summit just in time for the Nitto ATP Finals.

With one tournament left, here’s how the various scenarios could play out:

If Sinner Goes Undefeated in Turin

Despite holding the top spot entering Turin, the year-end No.1 ranking still largely rests on Alcaraz’s racquet, thanks to his consistent performances across the season. The Spaniard’s challenge, however, is that the ATP Finals has historically been his weakest event — it remains the only big tournament where he has a losing record.

If Sinner goes undefeated and wins all five matches (as he did in 2024), Alcaraz must either:

• Win all three of his round-robin matches, or
• Win two and reach at least the final to secure the year-end No.1 finish.

In the rare case that Alcaraz loses two group-stage matches but still qualifies for the semifinals, a run to the final would still be enough to retain the top ranking.

If, however, Alcaraz fails to advance past the group stage, Sinner would almost certainly claim the year-end No.1, capitalizing on both form and momentum.

If Sinner Loses One Round-Robin Match

Should Sinner win the ATP Finals but drop one match in the group stage, Alcaraz would need to win just two matches in total, regardless of whether he advances to the semifinals, to stay No.1 at year’s end.