Jannik Sinner will begin his bid to win the US Open next week in the wake of revelations that the 23-year-old, who is the men’s No 1-ranked tennis player, twice tested positive for a banned anabolic steroid in March.

It’s a case that no one knew about until Tuesday and one that has drawn all sorts of questions – and, in some instances, criticism – from other players who wonder whether there was a double standard at play because of Sinner’s success, are confused about why this was all kept under wraps, and want to know why Sinner was allowed to keep competing before there was a resolution.

“I will now put this challenging and deeply unfortunate period behind me,” Sinner said in a statement on social media. “I will continue to do everything I can to ensure I continue to comply with anti-doping [rules] and I have a team around me that are meticulous in their own compliance.”

Not everyone is completely ready to move forward. And it will be interesting to see how much scrutiny Sinner receives – from other athletes, spectators and the media – during the year’s last grand slam tournament, where he will be the top-seeded man.

“Different rules for different players,” 2021 Wimbledon semi-finalist Denis Shapovalov wrote on social media.

Who is Jannik Sinner?

Sinner is a rising Italian star who moved up to No 1 in the ATP rankings for the first time in June and is considered one of the leaders of the next group of tennis players who will succeed Roger Federer, Rafael Nadal and Novak Djokovic, if the latter ever stops playing and winning.

Sinner’s first grand slam triumph came in January at the Australian Open, where he eliminated Djokovic in the semi-finals before erasing a two-set deficit in the final to beat Daniil Medvedev. His most recent title came at the Cincinnati Open on Monday.

What is clostebol, the drug Sinner tested positive for?

Clostebol is an anabolic steroid that can be found in ointments and sprays sold over the counter in some countries, such as Italy, and is used to treat cuts or scrapes.

It is considered a performance enhancer, and several athletes in various sports have been suspended after testing positive; one high-profile example was baseball star Fernando Tatis Jr, who received an 80-game ban from Major League Baseball in 2022.

Sinner submitted a urine sample showing traces of clostebol during the Indian Wells tournament in California in March; an out-of-competition sample eight days later also tested positive.

How did Sinner explain away the positive test results?

Sinner’s lawyers said that his fitness trainer purchased a spray “easily available over the counter in any Italian pharmacy” which was given to the player’s physiotherapist, Giocomo Naldi to help treat a minor cut on the physio’s finger. Naldi regularly massaged Sinner during the Indian Wells tournament, without wearing gloves.

Sinner’s lawyers claimed that because the player had “various skin lesions” on his body due to a skin condition called psoriasiform dermatitis, the spray – which contained clostebol – must have passed from the physio’s hands through to Sinner and caused the “inadvertent contamination”.

Timeline according to independent tribunal report

12 February 2024: Sinner’s fitness coach, Umberto Ferrara, buys a spray used on cuts, branded Trofodermin, in a pharmacy in Bologna, Italy.

3 March: Physiotherapist Naldi cuts the little finger on his left hand while reaching into his treatment bag, nicking it on the scalpel he uses to treat calluses on players’ feet. He bandages the cut for two days. Witnesses provide discrepancies on exactly where and when the cut occurred but agree it was caused by the scalpel in the bag on 3 March.

Later that evening, Sinner asks about the bandaged finger during a session with Naldi. Naldi explains the cut and says that he has not treated it with anything.

5 March: Naldi removes his bandage and Ferrara recommends he use the Trofodermin spray for its healing qualities. Naldi does not check the contents, which include the banned substance clostebol. Naldi applies the substance to the small wound on his finger every morning for nine days, in the ensuite bathroom in the villa where they are staying in California.

5-13 March: Naldi gives Sinner a daily full-body massage using oils, and without wearing gloves, lasting an hour to an hour and a half. Naldi also performs foot exercises to assist with an ankle injury. The times of day vary.

10 March: Naldi applies two sprays of Trofodermin to his finger in the morning. He treats Sinner’s feet and ankle, where the player’s skin condition – psoriasiform dermatitis – has previously caused itching, leading to scratching and small cuts and sores. Naldi cannot remember if he washed his hands between applying spray to his finger and massaging Sinner.

That evening, after beating German player Jan-Lennard Struff in straight sets, Sinner submits two urine samples (primary and corroborative) at Indian Wells, which both test positive for clostebol.

16 March: Sinner is beaten by Carlos Alcaraz in the semi-finals of Indian Wells.

18 March: Another urine sample provided by Sinner, ahead of the Miami Open, tests positive for clostebol.

4 April: Sinner is formally notified of an adverse analytical finding (AAF) and the automatic provisional suspension is triggered. Sinner responds – on the same day – with an urgent application for the suspension to be lifted. His provisional ban is lifted the next day.

17 April: Sinner is notified of the second AAF. He responds with another urgent application for the automatic provisional ban to be lifted, and his application is upheld.

30 May: The International Tennis Integrity Agency (ITIA) charges Sinner with anti-doping rule violations.

19 June: Sinner’s legal team submits detailed explanations of the AAF.

20 August: ITIA reveals the case and its findings, announcing Sinner has been cleared of wrongdoing.

Why was Sinner allowed to continue competing?

Sinner was provisionally suspended for the two positive results but he appealed against those bans, saying that he was inadvertently exposed to the steroid.

Sinner’s appeal was submitted on the same day he was formally notified of the first adverse analytical finding (AAF), complete with a laboratory statement and written submissions from his support team. It is unclear whether he was given advanced warning of the AAF before being formally notified.

The ITIA, which handles anti-doping and anti-corruption investigations for the sport, accepted his explanation. The ITIA said it conducted a “thorough investigation” involving “multiple in-depth interviews” with Sinner and his support team. The ITIA’s investigators conducted 10 interviews in total and sought the expertise of three anti-doping experts.

It then passed the case to an independent tribunal to review the details of the case. A hearing was convened at Sport Resolutions on 15 August, which found that Sinner was not negligent and not at fault.

The independent tribunal consulted three scientific experts, including Professor David Cowan of King’s College London, the former head of the KCL’s Wada [World Anti-Doping Agency]-accredited lab. All three experts concluded that Sinner’s explanation was plausible.

They noted that Sinner tested for only small concentrations of clostebol. On 10 March, he tested for 121pg/mL of the substance, and on 18 March he tested for 122pg/mL. The Trofodermin spray contained 5mg/mL of clostebol acetate.

Professor Cowan said: “Even if the administration had been intentional, the minute amounts likely to have been administered would not have had ... any relevant doping, or performance-enhancing, effect upon the player.”

Was he punished at all?

Because one of the positive tests came during a tournament, Sinner had to forfeit $325,000 in prize money and 400 ranking points he earned by getting to the semi-finals at Indian Wells.

What do other players think about Sinner’s case?

Plenty of players hopped on social media to offer their takes on the latest high-profile doping case in tennis, a list that includes suspensions reduced on appeal for grand slam champions Maria Sharapova and Simona Halep.

Nick Kyrgios, the Wimbledon runner-up in 2022, called the situation “ridiculous” and said he thought a ban was warranted.

Tennys Sandgren, a two-time quarter-finalist at the Australian Open, said Sinner’s explanation for how the steroid got into his system “does seem pretty plausible” but added: “How this was handled really doesn’t seem fair compared to other players whatsoever.”

There also were those who noted that both Jenson Brooksby and Mikael Ymer were suspended for missing tests, as was Britain’s Tara Moore. The 19-month suspension effectively destroyed Moore’s career.

“I guess only the top players’ images matter,” Moore wrote on social media. “I guess only the independent tribunal’s opinion on the top players is taken as sound and right. Yet, they question them in my case. Just makes no sense.”

Chris Evert, the 18-time grand slam champion and ESPN analyst, said: “I do think that they protect top players. By ‘protecting’ – they’re going to keep the secret for a couple of months. 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. It’s all going to come out in three months, anyway.”

What did the ITIA say?

“We take any positive test extremely seriously and will always apply the rigorous processes set out by Wada. The ITIA carried out a thorough investigation into the circumstances leading to the positive tests with which Mr Sinner and his representatives fully cooperated.

“Following that investigation, the ITIA accepted the player’s explanation as to the source of the clostebol and that the presence of the substance was not intentional. This was also accepted by the tribunal.

“We thank the independent tribunal for the speed and clarity of its decision in relation to the player’s degree of fault.”

What did Sinner’s lawyers say?

“Anti-doping rules have to be very strict to be effective,” said Sinner’s legal representative Jamie Singer. “Sadly, the unfortunate consequence is that, occasionally, entirely innocent athletes get caught up in them.

“There is no question that Jannik is innocent in this case. The ITIA did not challenge that key principle. However, under strict liability rules, Jannik is responsible for whatever is in his system, even when entirely unaware of it, as in this exceptional case.”

Could the decision to clear Sinner be overturned?

The decision is subject to appeal by both Wada and the Italian Anti-Doping Agency (Nado Italia). The ITIA has said it will not appeal against the findings of the independent tribunal.

Additional reporting by AP