US Open in tennis: Jannik Sinner fires duo after avoiding suspension for failed doping tests

“They (Naldi and Ferrara) have contributed a lot to my career,” Sinner said at a press conference at the US Open on Friday.

“We did an incredible job, had a lot of success and had a great team behind us.

“Because of these mistakes, I am now not so confident about continuing with this. I have been struggling a lot in the last few months. I have been waiting for the result. The only thing I need now is clean air.”

The 23-year-old, who has Australian Darren Cahill as one of his two coaches, is scheduled to face his first-round opponent Mackie McDonald, an American ranked 140th in the world, on Tuesday.

The Sinner case has sparked a storm of indignation, considering that other players who fail doping tests are usually suspended during the investigation.

Sinner repeatedly protested his innocence and said he was able to continue playing because his team quickly identified the source of the contamination.

“I was only able to play because we knew where the substance was and how it got into my body,” he said. “It's very important to do this process, to inform them, and they understood immediately.”

When asked if he was concerned that the controversy would damage his reputation, Sinner said: “In my head, I knew I had done nothing wrong.

“Anyone who knows me well knows that I have never done anything and would never do anything that violates the rules.

“As far as reputation goes, we'll see how it goes, right? Because I have no influence over that.”

Current and former players have alleged a double standard and questioned why Sinner was not immediately suspended like other players who tested positive.

“Many players are going through the same thing and have to wait months or years for their innocence to be declared,” British player Liam Broady wrote on social media.

ESPN analyst and 18-time major winner Chris Evert said she believes high-level players like Sinner will face different consequences after testing positive.

“I think they protect top players,” she told reporters this week. “I think there's a certain level of protection there, like if you were Joe Smith, who's ranked 400th in the world.”

Sinner insisted that he receive the same treatment as his teammates.

“Any player who tests positive has to go through the same process. There is no shortcut, there is no different treatment, it is the same process for everyone,” he said.

“Of course, I know sometimes the frustration of other players. But maybe because they were banned, they don't know exactly where it came from, nor what substance it is. But the main reason is where it came from and how it got into his own body. We knew immediately.”