Jannik Sinner has been worn down “physically and mentally” by the investigation into his positive tests for a banned substance, says the world number one’s coach Darren Cahill.

The Italian twice tested positive in March for clostebol – a steroid that can be used to build muscle mass – but was cleared of fault or negligence by an independent tribunal last week.

The International Tennis Integrity Agency (ITIA) found Sinner was inadvertently contaminated with the substance by Giacomo Naldi, his physiotherapist.

Since first alerted about the doping violations in early April, Sinner has won tournaments in Halle and Cincinnati and become world number one for the first time in his career.

“I guess if you are not a Jannik fan, you may not see too much difference in what he has been doing the last few months because he has still been playing quite well,” Cahill told his ESPN colleague Chris McKendry.

“But if you are a Jannik fan, you would have seen a big change in his body language, physicality on the court, his excitement to be on the court – he’s struggled and I think it’s worn him down physically and mentally.

“He got tonsillitis, which is the reason why he missed the Olympics.

“I just want to stress that he’s maybe the most professional young man that I have ever had the chance to work with. He would never ever intentionally do anything, and he’s in a situation that is incredibly unfortunate.”

The World Anti-Doping Agency told BBC Sport it “will review this decision carefully” before deciding whether to appeal – an approach it takes in all such cases.

Some players have taken to social media to claim Sinner has been treated differently because he is the world number one.

And 18-time Grand Slam singles champion Chris Evert says she believes the authorities do protect top players.

“They’re going to keep certain things secret if you’re a top player because they don’t want the press, the player doesn’t want the press,” Evert said on a conference call before ESPN’s US Open coverage.

“I do think there’s some [more] protection there than if you were Joe Smith, ranked 400 in the world.”

Sinner’s lawyer has denied his client received special treatment.

“It’s perfectly reasonable to wonder that, but I think it’s actually the reverse,” Jamie Singer told BBC Radio 5 Live.

“Because he was such a superstar, the ITIA took it exceptionally seriously. But it was independent tribunals making those decisions, and that’s the critical piece here – nobody within tennis decided this, independent judges decided this.

“It’s had a huge impact on him. He’s been a different character over the summer, he’s been much more introverted.

“Jannik personally never did anything wrong. This is a mistake the physio made, and so he’s living with all of this scrutiny because a physio made a mistake.”