FORMAL allegations of possible anti-doping rule violations have been put to 34 current and former AFL players by the Australian Sports Anti-Doping Authority.

Sources confirmed to on Thursday night that the head of ASADA, Ben McDevitt, had been in contact with the AFL and the players’ solicitors. 

ASADA is expected to issue a media statement on Friday morning.

This latest development in the Essendon supplements scandal is significant because it’s the first time formal proceedings have begun against players.

In a statement on Thursday night, the Bombers said, “The Essendon Football Club is not in a position to comment on any matter relating to its players and the ASADA investigation.

"The club will continue to act in the best interests of its players and respect the integrity and confidentiality of this process."

The statement said Essendon chairman Paul Little would address the media on Friday afternoon.

The prospect of the case becoming tied up in legal proceedings for years looms large, however. 

Lawyer Tony Hargreaves, who is representing Essendon's players, told he hadn't seen any notices and was under instructions not to say anything.

The AFL had no comment on Thursday night.

Show-cause notices require players and officials to explain, within 10 days, why they should not be handed infraction notices for breaching the WADA drug code.

If ASADA doesn’t accept the explanation it then compiles a report on each player who may have breached the code.

This report is then given to an independent group of experts which assesses the evidence and decides whether an infraction notice should be issued by ASADA and the AFL. 

If an infraction notice is issued, the player would be suspended immediately until the matter was resolved at a Tribunal. Players face up to a two-year ban if found guilty of taking a prohibited substance. 

Essendon great Tim Watson told Channel Seven that "the players are in shock".

Watson said the players faced a huge challenge to get up for the clash against Melbourne on Sunday - and for the rest of the season.

"How they’re going to do that, I’ve got no idea," Watson said.

"What we will know very shortly is there will be some legal action launched by the Essendon Football Club, and what happens after that is anyone’s guess."

Watson said the saga could drag on for another two to three years.

Club great Matthew Lloyd believed Essendon's season is effectively over.

"One (season) has been ruined last year. This one is going to be ruined I would have thought, and who knows what next year brings?" Lloyd told radio station 3AW.

Earlier on Thursday, Essendon chairman Paul Little addressed the ASADA issue in a letter to members.

"Unfortunately there has not been any significant developments or relevant information made available to the club in recent weeks," he said.

"Our players are still carrying the heavy burden of continued speculation in the media with no concrete timetable for the ASADA process to conclude - this has been incredibly frustrating for us all.

"However, I can confirm we are exploring all legal options for our players in the unlikely event they receive show cause letters from ASADA.

"We make no apologies for that."

Essendon announced on February 5 last year that they were to be investigated under a joint AFL and ASADA inquiry.

In August last year, the AFL heavily penalised Essendon, kicking them out of the finals and suspending coach James Hird for 12 months among other punishments.

But the ASADA investigation has been ongoing.

Also last year, Essendon conducted its own investigation into the supplements program.

Investigator Ziggy Switkowski reported "a disturbing picture of a pharmacologically experimental environment never adequately controlled or challenged or documented within the club".