Another AFL footballer has tested positive on game day to cocaine and, judged by what we know about his case, we should be prepared for another battle between the player and ASADA.

Brayden Crossley has been adamant that he did not knowingly take cocaine, which has mysteriously found its way into his system and showed up in a game day test back in late May.

Crossley's problem is that the onus is on him to prove what happened. First of all, he needs to show that he didn't intend to cheat with a performance-enhancing drug. If he can demonstrate this fact, then his suspension is automatically cut in half, from a maximum of four years to two years.

This first step should be achievable. He is alleged to have ingested – by whatever means – an illicit drug that is only deemed performance-enhancing on game day. If the substance was detected at a very low level, then ASADA may well accept that he didn't take it with the express purpose of running faster and jumping higher.

The harder part will be to persuade the national anti-doping body that his use of the drug was inadvertent, further diminishing his level of fault. Athletes who show "no significant fault" have their sentences cut in half (so that might be from two years to one); those who demonstrate "no fault" walk completely.