Darren Cahill, Australia's tennis super-coach, has revealed that world No.1 Jannik Sinner will be the last player he coaches on a full-time basis.

Cahill, who has guided four different players to the world No.1 spot - Sinner, Lleyton Hewitt, Andre Agassi and Simona Halep - during a glittering career, joined forces with Simone Vagnozzi in 2022 to guide the exceptional Italian superstar.

The Adelaide mentor credits Vagnozzi as being Sinner's "main coach" and "main voice", saying "he's the one that delivers all the information."

But Cahill is the one who has brought all the experience after his experiences guiding the other world beaters -- though he reckons the remarkable 23-year-old Italian is likely to be the last.

At 59, Cahill says Sinner is the final player he'll coach "full-time." Asked how long he might continue with the Australian and US Open champ, he added: "Whatever he wants.

"There's always a right time to get a new voice, get new inspiration, a new set of eyes. ... but everything is going really well with us at the moment."

Giant billboard photos of Sinner grace nearly every piazza and street in Turin where he is hot favourite to lift the ATP Finals crown.

Fans have travelled from every corner of Italy to see him. The crowd chants his name before, during and after all of his matches.

For many other players, all of the attention — amid a pending doping case, too — might be too much to handle.

Not Sinner.

The humble tennis star from the German-speaking region of Alto Adige, who in the last year has overshadowed soccer players to become Italy's biggest sports star, just keeps on winning.

"You need to be a special type of person to be able to embrace all that pressure and come here and feel the pressure but still be able to perform at your very best," said Cahill.

"It's a huge step to be able to do what he's done in the last 12 months and to consistently do it time and time again.

"But the more you win against the best players in the world, the more belief you gain in yourself as a player. … It's been a great learning year for him."

Sinner's performance amid doping case has been 'inspirational', according to Cahill.

Sinner is playing at home in the ATP Finals for the first time since it was announced before his US Open title that he tested positive for an anabolic steroid in two separate drug tests in March.

A decision by an independent tribunal to clear Sinner of wrongdoing was appealed by the World Anti-Doping Agency in September and the Switzerland-based Court of Arbitration for Sport is expected to make a final ruling on the case next year.

"He's playing with a clear conscience and he's been doing it since April," Cahill said.

"We don't know what the future holds and we'll just keep trying to embrace him and support him. … He's been inspirational.

"To be working with him at the moment and to watch him accomplish what he's accomplished is pretty special."

Sinner's explanation was that the banned performance-enhancer entered his system unintentionally through a massage from his physiotherapist, who had used a spray containing the steroid to treat his own cut finger.

The spray was given to the physiotherapist by Sinner's fitness trainer.

Sinner fired the physiotherapist and fitness trainer and added two new members to his team, Marco Panichi and Ulises Badio, both of whom who previously worked with Novak Djokovic.

The real work with Panichi and Badio will begin after the season ends at the Davis Cup finals next week.

The only player capable of beating Sinner more than once this year has been Carlos Alcaraz, who won all three official meetings in 2024.

"Carlos and Jannik are going to play 70 times in the next 15 years," Cahill said.

"Every time you get a chance to step onto the court with Carlos it's a great opportunity to play against the best and to learn and keep improving. It's like going to school, doing your homework. Keep on learning and try to get better every time."

Sinner and Alcaraz have already played 10 official matches, with Alcaraz leading the rivalry 6-4.

If they did meet 70 times, that would break the men's Open era record of 60 meetings between Rafael Nadal and Novak Djokovic.

"The style of play they both have, the excitement, the joy they bring to the court, it's not just for us to sit there and be coaches of Jannik," Cahill said.

"We're fans of the game as well, so we get to enjoy that."

Cahill recently posted a photo on Instagram of Sinner driving Badio to practice on a red Vespa in Monaco.

Might driving a scooter around a city with streets of hairpin turns made famous by its Formula 1 race be risky for the top-ranked player?

"Most tennis players have a little bit of the risk factor in their lives," Cahill said with a laugh.

Sinner won junior titles as a skier before switching to tennis fulltime and also hits the slopes during the off-season.

"They play a fast sport. It's an emotional sport," Cahill added.

"So sometimes you have to relieve a little bit of tension. He's a very sensible young man and he's not going to do anything that's going to jeopardise his career long term."