Willie Rioli stands accused of one of the most serious offences under the World Anti-Doping Code; deliberately tampering with a urine sample.
Unless he can convince Australian Sports Anti-Doping Authority investigators or, more likely, an AFL tribunal, that he didn't do it, he faces a potentially career-ending, four-year ban.
Willie Rioli has been provisionally suspended by the AFL.Credit: AAP
The accusation against him is that he substituted his urine sample, an example of what WADA classifies as chemical and physical manipulation.
"If it is a substitution there is a degree of premeditation," says former anti-doping chief Richard Ings.
"It is very rare for a tampering case to get anything less than four years. You have got to be really sneaky, you have got to have a urine sample with you or some paraphernalia to swap it. It is almost aggravated behaviour when it happens."
Rioli was advised on Wednesday night that the "A" sample he provided to testers on August 20 showed evidence of tampering.
His first decision will be whether to ask ASADA to test the "B" sample he provided during the same testing mission. If the two samples match up, his next decision will be whether to cop the mandatory, four-year ban or contest the charge at a hearing.
He will be guided through this process by David Grace QC, the experienced sports lawyer who successfully defended before an AFL tribunal 34 current and former Essendon players accused of taking a banned peptide.
That decision was subsequently overturned by the Court of Arbitration for Sport.
There is a long, lurid history of athletes tampering with urine samples in failed attempts to beat drug testers.
One of the best known cases is the demise of Irish swimmer Michelle Smith de Bruin who, on the night she was paid a surprise visit at home by drug testers, attempted to slip a wee dram into her sample – presumably to mask the presence of a banned substance.
A lab analysis later revealed a concentration of alcohol "in no way compatible with human consumption" and a "very strong whiskey odour" emanating from the sample.
There are cases of athletes submitting samples from teammates and more elaborately, using fake penises pre-filled with clean urine to fool drug testers.
In a recent urine swap case, American basketballer DJ Cooper was questioned by anti-doping authorities after a sample he returned suggested he was pregnant.
His sample showed traces of gHC, a hormone naturally produced by the placenta. It was no joyous occasion for Cooper, who was hit with a two-year ban and later admitted to passing off his girlfriend's urine sample as his own.
The Sochi Winter Olympics saw sample-tampering on an industrial scale, when corrupt lab officials conspired with the Kremlin, cheating Russian athletes and secret service agents to swap dirty urine for clean samples through a secret "mouse hole" in the lab wall, in the dead of night.
The implications from that scandal and Russia's systematic cheating are still reverberating through Olympic sport.