ASADA says it's still waiting for the AFL's 'full investigation file' into the case involving Greater Western Sydney player Lachie Whitfield and former officials Graeme Allan and Craig Lambert.

The trio is being investigated over allegations Whitfield went out of his way to avoid drug testers early last year.

League chief executive Gillon McLachlan said he was optimistic of an outcome 'in the next week or so' when asked about the case at the fixture launch almost a fortnight ago.

On Tuesday morning, Fairfax Media reported there had been a delay.

Now, later on Tuesday, the anti-doping watchdog told AFL.com.au that it's League headquarters holding things up.

"On 31 October 2016, ASADA asked the AFL for its full investigation file, which we are still awaiting," an ASADA spokesperson told AFL.com.au.

"Because the potential consequences for individuals are so serious, it is important that ASADA considers all relevant material before any decision is made about whether to take forward possible anti-doping rule violations.

"In this case, as the information was collected as a part of an AFL investigation, due diligence requires ASADA to assess all evidence collected in its entirety."

With the cloud of investigation still hovering, Allan has since left GWS and joined Collingwood as football manager, while Craig Lambert is at the Brisbane Lions in a player welfare role.

Late on Tuesday, the League said it had provided its 'investigation brief' to ASADA on 1 September 2016.

"ASADA then asked the AFL in the last week for further information, material relating to the AFL’s investigation and the AFL is now in the process of compiling that material and getting it to ASADA as quickly as possible," AFL spokesman Patrick Keane said.