THE AFL has conceded that the player who is the subject of an Australian Crime Commission investigation in relation to performance-enhancing drug use may play in the NAB Cup.

AFL CEO Andrew Demetriou said on Monday he did not know the identity of the player being investigated alongside multiple Essendon players, or whether he was a current or former player.

After receiving clarification from the ACC on Monday morning, Demetriou also said he was unable to notify the club it had a player under investigation.

"We are doing our very best to be transparent on these issues, but it's a special set of circumstances and we must comply with the parameters being put upon us by the Australian Crime Commission and its legislation," he said.

Demetriou said the AFL would be kept in the dark if a player tested positive to performance enhancing drugs at any time, while an investigation was being completed.

"There is that chance [that the player is playing in the NAB Cup], but what I'd say is, in normal circumstances if a player had tested positive to performance enhancing drugs, ASADA would be conducting an investigation in private and we wouldn't know about it, and there's a potential that a player would be playing in that situation," he said.

"If they are found to be guilty of using performance enhancing drugs, they will be dealt with under the WADA code, and it's exactly the same in this situation."

AFL ups ante in fight against drugs

Demetriou said he would prefer to be able to contact the second club involved, and would be seeking permission from the ACC to do so.

In the meantime, Demetriou said the League had only been able to notify clubs identified in the ACC report as "vulnerable" to either performance enhancing or illicit drugs.

Demetriou said the ACC may have contacted the club or the player directly.

He would not be drawn on whether he would prefer the second club to go public if it had been approached by authorities about the suspicion over one of its players.

"It's very important in the light of the uncertainty that ASADA is free to conduct its investigation as it would normally, to do it diligently, that we co-operate with them, that the club and player in question co-operate with them, and that it's dealt with so that everyone knows who the player is, and they're dealt with under the WADA code," Demetriou said.

League officials could face financial penalties or even jail time if they breach strict confidentiality agreements with authorities.

Speaking at the launch of the NAB Cup, Demetriou said he hoped the drugs in sport scandal would not overshadow the start of the pre-season competition.

"I want to stress to all our supporters that whether it's the NAB Cup or the premiership season, come along and watch their football, and have faith in the game, because this is not a widespread problem relating to performance enhancing drugs in our code," he said.

The NAB Cup starts at Etihad Stadium on Friday night with a lightning round robin between the Bombers, the Western Bulldogs and Collingwood.