Following his defeat to Carlos Alcaraz in the US Open final, Jannik Sinner began to work on his serve.
The Italian’s serve was well below par during his defeat on Arthur Ashe Stadium, making just 48% of his first serves in the US Open Championship match.
Leaked training footage showed Sinner focusing on his serve during practice in the days that followed, as the world number two clearly identified the shot as an area of weakness.
It looked as though the hard work paid off when Sinner won the China Open in his first tournament back, defeating Learner Tien in the final.
However, reacting to Sinner’s latest triumph, his fellow Italian has identified an area of the 24-year-old’s game that has regressed while he tweaks his serve.
Paolo Bertolucci has noticed Jannik Sinner’s serving speed decrease
Writing for La Gazzetta dello Sport, Italian tennis legend Paolo Bertolucci highlighted the two changes Sinner has made to his serve.
“To improve his serve, a shot he’d hit hard in New York, Jannik [Sinner], a seasoned pro, worked hard, focusing on a couple of things with his coach Simone Vagnozzi,” said Bertolucci.
“One was his toss, which was a bit too advanced, and he tried to bring it closer to him.
“The other was related to his swing, as there was some dispersion, with a slightly too pronounced pause at the bottom of the racket.
“This action has been shortened and abbreviated: the racket head now comes up earlier, allowing for a less dispersive, faster execution that encounters fewer difficulties at impact.”
Bertolucci explained the effect these changes have had on Sinner’s serving speed.
“It’s a swing designed to have a slightly more consistent first serve, but more than the speed itself, the focus has been on his slices: the ball is certainly now being smeared and new directions are being sought, but to do this, as is only natural, he had to reduce his cruising speed a bit,” he said.
Sinner won’t be too concerned about a reduction in serve speed if the rest of his numbers improve, however.
But did the stats show any real improvement from the US Open to the China Open?
Jannik Sinner’s serving stats at the US Open and China Open compared
Sinner’s serve cost him in New York, producing some of his worst numbers of the year in the final.
Jannik Sinner’s 2025 US Open serving stats
| Round | Aces | Double faults | 1st Serve % | Win % on 1st Serve | Win % on 2nd Serve |
| F vs Carlos Alcaraz | 2 | 4 | 48% | 69% | 52% |
| SF vs Felix Auger-Aliassime | 11 | 4 | 53% | 76% | 72% |
| QF vs Lorenzo Musetti | 10 | 0 | 61% | 91% | 52% |
| 4R vs Alexander Bublik | 8 | 1 | 58% | 81% | 76% |
| 3R vs Denis Shapovalov | 2 | 5 | 59% | 85% | 55% |
| 2R vs Alexei Popyrin | 6 | 4 | 55% | 78% | 67% |
| 1R vs Vit Kopriva | 7 | 1 | 57% | 82% | 57% |
| Tournament average | 7 | 3 | 56% | 80% | 62% |
His numbers stayed relatively consistent in Beijing, although there was a significant improvement from how he performed in the US Open final.
Jannik Sinner’s 2025 China Open serving stats
| Round | Aces | Double faults | 1st Serve % | Win % on 1st Serve | Win % on 2nd Serve |
| F vs Learner Tien | 10 | 1 | 66% | 77% | 59% |
| SF vs Alex de Minaur | 7 | 0 | 64% | 82% | 46% |
| QF vs Fabian Marozsan | 7 | 1 | 57% | 70% | 64% |
| 2R vs Terence Atmane | 3 | 0 | 63% | 69% | 47% |
| 1R vs Marin Cilic | 3 | 0 | 77% | 75% | 64% |
| Tournament average | 6 | 0 | 65% | 75% | 56% |
Sinner will hope to improve his serve further when he returns to action at the Shanghai Masters.
The defending champion will play Germany’s Daniel Altmaier in his opening match, a man he has played twice before.
- 2023 French Open 2R – Daniel Altmaier defeated Jannik Sinner, 6-7, 7-6, 1-6, 7-6, 7-5
- 2022 US Open 1R – Jannik Sinner defeated Daniel Altmaier, 5-7, 6-2, 6-1, 3-6, 6-1
Looking to take the lead in their head-to-head, Sinner will play Altmaier in the second round of the 2025 Shanghai Masters on Saturday, October 4.
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