What is the substance and how serious an offence is this?

The International Tennis Integrity Agency (ITIA) does not consider this a serious offence. TMZ is a drug primarily used as heart medication and has been involved in several high-profile doping cases. However, the ITIA ruled Swiatek did not intentionally take the banned substance and that her level of fault in the positive test was the “lowest end of the range” for no significant fault or negligence.

The ITIA accepted that the positive test was caused by the contamination of the non-prescription medication Swiatek had been taking – melatonin – to address jet lag and sleep problems. Melatonin is a regulated medication in Poland.

During the investigation, the ITIA sent a pack of melatonin provided by Swiatek and an unopened pack from the same batch for tests in an independent, Wada-accredited laboratory in Utah. Tests confirmed the substance was contaminated with TMZ and that was verified by an independent scientific expert from another Wada-accredited lab.

Why are we only finding out now?

As is standard in anti-doping cases, Swiatek received a mandatory provisional suspension on 22 September upon notification of the anti-doping rule violation and she was forced to withdraw from the Korea Open, China Open and Wuhan Open. After three weeks, however, Swiatek successfully appealed against her provisional suspension, which allowed her to return to competition before her case was resolved. Swiatek ended her season by competing at the WTA Finals in Riyadh and the Billie Jean King Cup Finals in Málaga.

This case has similarities and differences to the decisions in Jannik Sinner’s anti-doping case. Sinner also received a mandatory provisional suspension for each of his two positive tests for the banned substance clostebol, but since he was able to quickly identify the alleged source of the positive tests, Sinner immediately lodged an appeal both times and both suspensions were lifted in days. Swiatek also appealed swiftly but the process, which included the laboratory tests, took longer. She was also successful when she did.

It is rare for provisional suspensions to be lifted but an athlete can appeal against their provisional suspension at an urgent hearing if their argument rests on contamination or the case involves a substance of abuse, such as cocaine. If an athlete appeals against a mandatory provisional suspension within 10 days of receiving notice and the appeal is successful, the provisional suspension is not publicly disclosed according to the tennis anti-doping rules.

In many other cases, however, the athlete either accepts their provisional suspension or their appeal is unsuccessful, meaning they are ineligible to compete until their case is resolved.

What does it mean Swiatek and the way tennis is handling anti-doping cases?

Swiatek’s one-month ban includes the three-week provisional suspension she has already served, meaning she has seven days to serve and she will be free to compete again from 4 December. The WTA season has finished and it restarts on 27 December so this will not significantly affect her schedule.

Swiatek’s and Sinner’s anti-doping cases represent two of the most high-profile cases in the sport’s history, with both players ranked No 1 at the time. Both times, the players were able to successfully overturn their provisional suspensions and compete without disclosing their positive tests. The ITIA may come under further pressure to review their rules surrounding provisional suspensions.