Roger Federer and Rafael Nadal have different opinions about Jannik Sinner testing positive for a banned substance and escaping a suspension because the authorities believed it was unintentional.

While both Federer and Nadal believe that Sinner didn't use the banned substance knowingly, the Swiss great said that authorities have questions to answer about a perceived double standard applied to current world No. 1. But the Spaniard doesn't think that Sinner received any preferential treatment.

In March, Sinner tested positive for the steroid clostebol but was cleared by the International Tennis Integrity Agency after it was learnt that his physio applied a spray to a cut on his own hand before carrying out treatments on the Italian.

In an interview with NBC's Today show on Tuesday, Federer said: "It's not something we want to see in our sport. This type of news, regardless of whether he did something or not ... It's just noise that we don't want.

"I understand the frustration about whether has he been treated the same as others, and I think this is where it comes down to.

"I think we all trust pretty much that Jannik didn't do anything, but the inconsistency potentially that he'd have to sit out while they were not 100 per cent sure about what was going on, I think that's the question here that needs to be answered."

Nadal, on the other hand, told a Spanish television show that he did not believe that the decision about Sinner had anything to do with his world No. 1 ranking.

“I trust that he wasn’t punished because those who judged this case determined quite clearly that there was nothing to punish. ... I don’t believe the sentence has anything to do with him being No. 1 in the world,” Nadal said.

Before the US Open began, Novak Djokovic had also spoken about the inconsistency in such rulings.

Nadal, who sat out the US Open, said: “I have a virtue or a deficit, which is that in the end I usually believe in people’s good faith. I know Sinner, I don’t believe that Sinner has ever wanted to dope.

“I don’t think we have to like it only when it is resolved in the way we think. In the end, justice is justice and I believe in justice. I believe in the bodies that have to make decisions.”

Nadal said the anti-doping organisations must be trusted.

“I’m totally confident that if he has not been sanctioned it is because those who have had to judge this case have seen very clearly that there were no sanctions to be imposed. I do not believe that because he is Sinner he will not be sanctioned and because he is someone else he will be sanctioned. I really believe it and I am convinced of it."