WEST Coast forward Willie Rioli has returned a positive sample for a metabolite of cannabis in a separate ASADA test to that currently under investigation for urine substitution.

Rioli was tested following the Eagles' elimination final victory over Essendon on September 5.

His sample contained the metabolite of cannabis, which is an in-competition prohibited substance under the Australian Football Anti-Doping Code.

Read the AFL's statement on Willie Rioli here

It comes after he allegedly substituted urine during an out-of-competition doping control test on August 20.

He is currently provisionally suspended while that investigation takes place and is facing a ban of up to four years.

Rioli's provisional ban kept him out of the Eagles' semi-final against Geelong and rocked West Coast just two days out from the season-ending loss.

The 24-year-old returned to the Northern Territory after the news broke and his future in the game is under a major cloud after his latest adverse analytical finding.

"As stipulated two weeks ago, the club's primary concern remains the health and wellbeing of Willie," the Eagles said in a statement.

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"We will continue to support him through this particularly challenging time to assist him while this ongoing investigation runs its course.

"The club will respect the process of the investigation into the circumstances surrounding this case and will co-operate fully with it.

"We expect that these processes will take some months to complete and the club will not be in a position to make further comment until such completion."

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Former ASADA chief Richard Ings said because Rioli's positive cannabis sample was taken before he was notified of his alleged substitution on September 11 the cases are considered concurrent, and not consecutive, matters.

"So (Rioli) is still facing one consequence," Ings tweeted. "Whichever is worse."

Rioli has played 38 AFL games, including the 2018 Grand Final triumph, since he was the 52nd overall selection at the 2016 draft.