Novak Djokovic suffered his first defeat since Wimbledon, but it took a quite phenomenal performance from fast-rising Italian star Jannik Sinner to cause the upset.

Sinner was playing in front of a home crowd at the ATP Finals in Turin, and the exuberant fans helped to give him the extra push he needed to seal a 7-5, 6-7, 7-6 victory in 3hr 9min.

Djokovic, by contrast, was on the wrong end of some serious barracking. But he treated the brickbats with a sense of humour, often gesturing to the crowd to give him more.

These two have been the form players on the tour over the last few months, each winning multiple titles without coming up against each other. In Turin, however, they were drawn in the same round-robin group – which Sinner now tops after beating Stefanos Tsitsipas in his opening match.

The quality was remarkable. Data from the match showed that Djokovic was exceeding 80mph on 80 per cent of his forehands, which Is almost unheard of. Sinner was perhaps not applying quite as much muscle, but he takes the ball so early that he was still able to rush his opponent.

He also mixed in variations from time to time, which was an encouraging development after his critics had previously accused him of being too metronomic and predictable. We saw some well-timed net-rushes and several deft drop-shots, which broke up Djokovic’s pounding rhythm.

“I was really brave and I took my chance in important moments,” said Sinner, who did indeed keep playing eyeballs-out tennis even when the pressure was at its highest. This is the only way to take down a player of Djokovic’s class, as Carlos Alcaraz demonstrated at Wimbledon.

At 21, Sinner is a year older than Alcaraz. These two have been the only players this season to suggest that Djokovic might be beatable in the biggest matches, but they have not performed at the same time. Sinner started the season slowly, while Alcaraz has been largely ineffectual since Wimbledon.

Djokovic will play replacement Hubert Hurkacz on Thursday in his final group match, after Tsitsipas withdrew from the tournament through injury.