When Jannik Sinner walked off Arthur Ashe Stadium in September having lost the US Open final to Carlos Alcaraz in four sets, he did not mince his words. He had been predictable. He knew it, Alcaraz knew it, and now his coaching team had to do something about it.
What followed was one of the more deliberate technical reinventions the tour has seen from a player already at the summit of the game. Speaking in Turin after Sinner defended his Nitto ATP Finals title — beating Alcaraz again in the final, 7-6(4), 7-5 — coach Simone Vagnozzi spelled out exactly what changed.
“For sure after the US Open we saw some issues, especially with the serve,” Vagnozzi said. “We changed the motion. We changed the rhythm.”
The results were immediate. Sinner served well from Shanghai through to Turin, lifting titles in Beijing, Vienna, Paris, and at the season finale itself.
Darren Cahill, who coaches Sinner alongside Vagnozzi, put a finer point on the philosophy behind the work. “You have control over one shot in tennis, and that is the serve,” the Australian said.
“Jannik and Simone have done some incredible work over the last four or five weeks to rejig the serve and find that rhythm and tempo where he has been able to up the first-serve percentage.” Cahill was quick to stress the aim went beyond percentage points alone — the goal was a more potent, more varied weapon.
The numbers backed them up. Sinner won 713 of 775 service games across the season at a 92 per cent hold rate, becoming the first player in ATP history — since statistical records began in 1991 — to lead the Tour in both percentage of service games won and return games won across a single season.
Vagnozzi had signalled as far back as the lead-up to the ATP Finals that the serve improvements were part of a broader evolution. Speaking via Ubitennis before the Turin event, he noted that Sinner’s delivery had become more precise and effective since the US Open, with the Italian managing to land more kick serves and work the body more consistently.
“He goes to the net more often; in short, there are small details that have been improving over the last two years,” Vagnozzi said. “When Jannik is 27 or 28, he will be an all-around player.”
The serve overhaul paid its most visible dividend on the biggest stage. At the ATP Finals, Sinner won 84 per cent of his first-serve points against Alcaraz on his way to a perfect 5-0 week without dropping a set, earning a record champion’s payout of $5,071,000.
Vagnozzi was already looking ahead after Turin, noting that the goal for the next season would be for Sinner to play even more aggressively than he had in 2025.
For the Italian, the defeat in New York appears to have been less a setback and more a turning point. The willingness to acknowledge a flaw, strip back the mechanics, and rebuild while still winning titles is the kind of response that tends to worry rivals for years to come.
