Time is running out for appeals to be filed in the case that exonerated freshly-crowned US Open champion Jannik Sinner from doping.

The World Anti-Doping Agency (Wada) and Nado Italia, Italy’s anti-doping agency, likely have only one more day to challenge the decision announced by the International Tennis Integrity Agency (ITIA) on August 20.

There is a 21-day window to appeal that started when the parties received the decision. Any appeal would be filed to the Switzerland-based Court of Arbitration for Sport (CAS).

Sinner tested positive twice for an anabolic steroid in March but was not suspended because the ITIA determined the banned performance-enhancer entered his system unintentionally through a massage from his physiotherapist.

The doping case was kept secret until last month’s announcement and the top-ranked Sinner went on to beat Taylor Fritz in the US Open final on Sunday.

An appeal could jeopardise his US Open title but Sinner and his legal team have provided detailed scientific evidence to show that his explanation is credible.

An appeal verdict at CAS could come quickly — even within just a few months — if the parties agree to cooperate. At least that’s how it worked in another high-profile doping case in tennis involving Maria Sharapova.

Sharapova tested positive at the Australian Open in January 2016 for the newly-banned heart medication meldonium. She was banned for two years in June that year by the International Tennis Federation.

The Russian star appealed to CAS, had an appeal hearing in New York before three judges that September, and four weeks later got the verdict that cut her ban to 15 months.

The entire process for Sharapova with CAS took just four months — far shorter than most doping cases, which typically last about one year. The timeline can stall with the complexities of picking a judging panel, finding a hearing date and parties exchanging documents and evidence from expert witnesses.

If Sinner did lose in an appeal case to CAS, he would likely face a maximum ban of two years instead of four. Four-year bans are usually reserved for athletes unable to show their positive doping test was unintentional.

Sinner provided a clear explanation to an independent tribunal in London, which judges cases brought by the tennis integrity body.

Any possible ban would likely be backdated to March.