West Coast's AFL finals campaign has been plunged into turmoil after premiership star Willie Rioli was banned for an alleged anti-doping breach.
Rioli faces a suspension of up to four years after returning an adverse analytical finding for urine substitution in a routine ASADA test.
The potential violation of the AFL's anti-doping code was detected after an out-of-competition doping control test on August 20, with ASADA informing the AFL on Wednesday.
While the A-sample didn't return any evidence of a banned substance in Rioli's system, the finding was that there was evidence of urine substitution, which is known as a "prohibited method".
Rioli was formally notified late on Wednesday night on his arrival in Melbourne with the rest of the Eagles team set to face Geelong in a knockout semifinal at the MCG on Friday night.
The 24-year-old has been officially withdrawn from that line-up.
AFL general counsel Andrew Dillon announced the ban at a press conference at AFL House in Melbourne.
"The provisional suspension is effective immediately," Dillon said.
"Rioli will not be eligible to compete in AFL competitions or any WADA-compliant sport, including the WAFL, while provisionally suspended.
"He will be able to train prior to final determination of the asserted code violation.
"It is important that Rioli is provided a fair process. As a result the AFL won't be providing further detail on this case at this time."
Rioli's shock suspension is a significant setback for the Eagles on the eve of their do-or-die final against the minor premiers.
"The club is extremely disappointed that one of our players has been provisionally suspended while a matter is being investigated and it will comply fully and openly with ASADA and the AFL through the process," a West Coast statement released on Thursday read.
"The club is fully committed to supporting Willie during what is a personally distressing time.
"Our primary concern is Willie's health and welfare.
"As this is an on-going investigation the club, its staff and players can make no further comment until the investigation is completed.
"The West Coast Eagles fully supports the AFL and ASADA in its ideal of our game being drug free."
Rioli has played 38 AFL games, including the 2018 grand final win over Collingwood, since he was the 52nd overall selection at the 2016 draft.