He has been provisionally banned under the AFL's anti-doping code for an "adverse analytical finding for urine substitution". He has not returned a positive drug test, rather a sample that was subsequently found not to be urine.

Rioli, the first AFL player to be accused of tampering with a urine sample, is with family away from the squad as the Eagles prepare for the cut-throat match and is not expected to take any part in the finals.

West Coast's football manager Craig Vozzo said Rioli was "a little bit of a mess, to be honest, emotionally" and was not in a good space.

The AFL's general counsel Andrew Dillon said an adverse analytical finding for urine substitution was a prohibited method under the code and could carry a four-year ban if the alleged action was found to be intentional, however the penalty could be reduced if mitigating circumstances are proved.

The sample was taken on Tuesday August 20, two days after the Eagles played Richmond in their round 22 clash at the MCG and tests subsequently discovered the sample was not urine.

Under WADA rules, the doping control tester is meant to have an unobstructed view of the sample leaving the athlete's body. The fact an alleged substitution may still have occurred with strict protocols in place has raised the question of how the sample could have been substituted with a substance other than urine.

ASADA informed the league of the results on Wednesday this week, and Rioli was notified on Wednesday night after arriving in Melbourne, having played in the final round against Hawthorn and the elimination final against Essendon.

The AFL released a statement on Thursday saying Rioli would not be eligible to compete in AFL competitions or any WADA-compliant sport (including the WAFL) while provisionally suspended. However, he will be able to train "prior to final determination of the asserted code violation".

Sources suggested Rioli had not yet been interviewed by either ASADA or the AFL integrity unit.

Vozzo said Rioli had left the Eagles' travelling squad and had not been in a state to give the club much information about what had happened. However, he confirmed that "something other than urine" had been produced by Rioli.

"Look he's very, very flat, the club and staff are really worried about his wellbeing, he's not in a great space," Vozzo said.

He said even if Rioli had not been provisionally banned, he would not have been in a state to play in Friday night's semi-final.

Vozzo said David Grace QC would be lead counsel on the case and that they had started preliminary discussions, but that Rioli had not been able to give them detailed information yet.

He described Rioli as "a wonderful young man we love and respect" and said his Eagles teammates were very emotional, but he was confident they would be able to compartmentalise.

He confirmed the club had been informed by an AFL investigator after landing in Melbourne on Wednesday night.

Vozzo acknowledged the difficult period in the club's history, which involved an alleged culture of illicit drug use among players and led to Ben Cousins being deregistered.