The AFL career of Fremantle utility Ryan Crowley could be over – and it’s all because of a painkiller.

Crowley’s future hangs in the balance after he tested positive to a banned substance following the club’s round-17 win over GWS last year.

The 31-year-old was issued with a show-cause notice by ASADA in September, at which time he accepted a provisional suspension.

The 2012 best and fairest winner is expected to face the AFL’s anti-doping tribunal within the next month to plead his case.

Crowley, who considered retirement after being notified of the positive reading, is facing a suspension of up to two years.

The 188-game veteran battled back problems last year, and he underwent surgery following the club’s exit from the finals.

Dockers chief executive Steve Rosich said it was believed the banned substance was contained in a painkiller that Crowley sourced himself.

“The painkiller was not prescribed by a Fremantle staff member or club doctor,” Rosich said.

Rosich said he was shocked when he was told in late October that Crowley had failed a doping test.

The AFL’s anti-doping tribunal and ASADA take a dim view on any doping breaches – even if they are accidental.

St Kilda’s Ahmed Saad was suspended for 18 months in November 2013 after testing positive for a banned substance, believed to be contained in an energy supplement drink.

ASADA was unsuccessful in their bid to have the penalty raised to two years on appeal.

Crowley is already in the tail-end of his career, and anything more than a six-month ban could force him to hang up his boots.

It remains unclear what Crowley tested positive for.

Crowley’s mysterious absence from pre-season games drew widespread questions last week, but the ASADA revelations have shed light on the matter.

His acceptance of a provisional suspension is not an admission of guilt or wrongdoing, but it does mean any ban will be backdated from September last year.

Should Crowley be suspended, it would be a huge blow to Fremantle’s flag hopes.

Crowley has established himself as the competition’s premier tagger over the past three seasons, and his potential absence means Matt de Boer is likely to be thrust into the shut-down role.

Defender Zac Dawson (groin) and Hayden Ballantyne (calf) are others set to miss the start of the season, while Colin Sylvia is unlikely to play for the Dockers again after being exiled to WAFL club Peel Thunder for poor training standards.

Crowley, who has appointed independent legal advisers to assist him with the matter, read out a brief statement on Monday.

“I would like to thank my partner Samara, my family and the club for their support over the past few months. It has been invaluable,” Crowley said.

“I have been overwhelmed by the number of inquiries and messages from members, fans and friends. Thank you, I really appreciate it.”

The revelations surrounding Crowley is another hit to the AFL, who are still dealing with the long-running drugs controversy surrounding Essendon.

HOW THE CROWLEY SAGA UNFOLDED *July 13, 2014 – Sample collected after win over GWS

*August 11, 2014 – Sample tested

*August 18, 2014 – Player notified of positive A sample

*September 11, 2014 – B sample tested

*September 18, 2014 – Show-cause notice (including notification of positive B sample) sent to Crowley

*September 25, 2014 – Voluntary provisional suspension accepted

*October 1, 2014 – Infraction notice served