Reports have surfaced that it was Whitfield’s ex-girlfriend who originally flagged the issue with ASADA, not the club as previously reported.

The 2012 No.1 draft pick is being investigated for allegedly seeking to avoid drug testers in May 2015 by staying at former Giants welfare boss Craig Lambert’s house.

McLachlan, addressing media at the launch at of the AFL finals in Melbourne on Wednesday, said he expected the investigation to be completed in coming days after the evidence had been handed to ASADA.

"In August (2015) the investigation started and as I understand it, it's been an incredibly detailed, forensic investigation," he said. 

"There haven't just been simple interviews. There's been forensic orders involved, retrieval of laptops and trying to get to the bottom of it. 

"These things take what they take. They work methodically through it and they don't rush to reach to an outcome." 

If found guilty, Whitfield could spend up to four years on the sidelines. 

"The way our process works I didn't have any visibility with it. I was briefed yesterday and it's now known the guys will finish that in the coming days," McLachlan said.

"The report and investigation and what they've compiled will be handed over to ASADA for them to make a decision and I can't really say more than that."