Collingwood's Sam Murray fronted the AFL Anti-Doping Tribunal on Thursday, more than a year after a positive ASADA match-day test.

The 21-year old Pie has effectively served a 12-month provisional suspension. He is facing a four-year ban under current rules, but is hoping to mitigate that sanction significantly.

Members of the Tribunal will deliberate over the next two weeks before releasing their findings.

Murray played 13 matches for Collingwood last year. He remains on the Pies' rookie list.

He was tested by ASADA late July 2018 and stood down two weeks later.

Sam Murray training with Collingwood in August, 2018. Picture: AFL Photos

AFL chief Gillon McLachlan said Murray's provisional ban would mitigate whatever sanction he eventually received.

"He's still on a provisional suspension now, and whatever he's served will count toward whatever it ends up being," McLachlan told radio station 3AW on Friday.

"That's the potential sanction. But there's mitigation and whatever argument they mount. It could be something less but it may be four (years)."

Details of the hearing have been kept confidential but McLachlan said Murray's case was being heard by a former Supreme Court judge.

Collingwood duo Josh Thomas and Lachie Keeffe received two-year doping bans in 2015 after testing positive to the banned substance Clenbuterol.

Keeffe was delisted by the Magpies and picked up by GWS in 2017, while Thomas remains at Collingwood and has played 18 games this season.