Bailey Smith has apologised after images emerged showing the Western Bulldogs star with an "illicit substance".
The images, which the Bulldogs say were taken in late 2021 after the season concluded, appear to show Smith holding a small plastic bag containing white powder.
"We are extremely disappointed to have observed social media content showing Bailey Smith with an illicit substance," Bulldogs chief executive Ameet Bains said in a statement.
"We absolutely do not condone our players being involved with illicit substances and firmly believe players are well-educated on what constitutes appropriate behaviour."
Smith has become one of the team's most important players since being drafted in 2018.
"I have recently been made aware of the presence of social media content that shows me with an illicit substance," Smith said in a statement.
"After much reflection, I am now in a position to confess to indulging in behaviours in late 2021 of which I am deeply ashamed.
"I do not have an excuse for those behaviours, however the state of my mental health over that period post Grand Final dramatically deteriorated, and I spiralled out of control leading to poor decision making and actions at the time.
"The depth of my emotions over that period, coupled with some of my behaviours, have reminded me that, as a person, I am still very much a work-in-progress."
Smith took time away from football after the 2021 season for mental health reasons, and the Bulldogs said "while this clearly does not excuse his behaviour, it is our responsibility as a club to ensure we have supported, and we continue to support, Bailey's health and wellbeing".
"The club has supported Bailey through this process, and we will continue to work closely with him and provide him the support he needs, as he continues his journey as a Bulldogs player," Bains said.
The AFL says it will interview Smith in the coming days "in relation to the emergence of the content on social media and the context surrounding it".
The AFL Players' Association said Smith had made a mistake, but "has put steps in place to learn from it and grow as a person as a result of it".
"When issues such as this arise, there are typically two alternative approaches people think should be taken," AFLPA chief Paul Marsh said.
"Condemn, sanction and shame the player involved, or support, educate and try to use the issue as an opportunity for growth.
"The AFLPA will support Bailey through this time, and we are confident the Western Bulldogs will do likewise."
Clothing giant Cotton On said it will continue sponsoring Smith "during this tough time".
"Although we do not condone his recent behaviour, we will stand behind him," the brand said in a statement.
The midfielder is currently midway through a two-game suspension for headbutting Geelong defender Zach Tuohy.
It was the first time he had been reported to the AFL's match review office.
The Dogs have a bye round this week and are not due to play again until next Saturday's game against the Greater Western Sydney Giants.
