AFL players are being warned by clubs that they can test positive on match day as much as seven days after taking an illicit drug and potentially earning bans of up to four years under the tough WADA code.

Some club doctors and football department officials have passed on the message to players that the detection capability of the ASADA laboratory that tests the players has improved to the point that they can test positive to the use of drugs such as cocaine seven days after it has been taken.

In November, the AFL's chief medical officer Dr Peter Harcourt told club doctors that players could be detected for illicit drug use within seven days of use. This message, intended for the doctors to pass on to players, has been communicated at different stages over summer by various clubs.

Harcourt's warning followed the positive test to cocaine by Collingwood defender Sam Murray in August, in a case that is in the hands of ASADA. Murray, who is training with Wangaratta Rovers, remains under provisional suspension as his legal team continues discussions with ASADA.