ESSENDON captain Jobe Watson has made the stunning admission that he believes he took the banned substance AOD-9604, but the AFL's reigning Brownlow medallist remains adamant he did nothing wrong.

The star onballer said on Monday night he took what he believed to be the anti-obesity drug after signing a consent form.

"I signed that consent form and my understanding, after it being given through (club doctor) Bruce Reid and the club, that I was receiving AOD," he told Fox Sports' program On The Couch.

Asked if he thought the substance was legal when he was taking it, Watson said he believed "that it was legal at the time and that was actually what I was told I was being given."

Essendon is under Australian Sports Anti-Doping Authority (ASADA) and AFL investigations for last year's supplement program.

The AFL hopes ASADA will announce its findings in early August.

AOD-9604 has emerged as a major factor in the controversy.

The World Anti-Doping Authority issued a statement early last month saying the drug was a banned substance.

Watson admitted that clarification surprised him.

"It did, because the understanding we had through the advice we got and through the medical doctor at the football club, that it was a legal substance," he said.

Watson and other players have fronted investigators to answer questions about the supplements program.

Despite the potential for ASADA to hand down severe sanctions, Watson is confident about his fate.

"I don't have a feeling of guilt and I don't believe I've done anything wrong," he said.

"So all I want is the truth to come out.

"It's not impacting on me, because ... it's not a cloud having over me.

"I don't care how long it takes."

Watson also admitted he was surprised by the number of injections he received in the supplements program.

"I don't know it was that vast, in terms of the numbers being reported," he said.

"As a player myself, it was a new frontier for us.

"Having that many injections was something I had not experienced in AFL football before."

Watson was interviewed before former player Mark McVeigh, who expressed concern after his interview about possible health effects of the supplements they were given.

"I wasn't surprised - I certainly had a different take to Mark," Watson said.

"There was a mention about fertility and things like that. That was news to me."

Watson admitted the anti-doping interviews had affected the players' on-field form at times, but overall they were sticking together.

Essendon has coped remarkably well with the stress of the investigations and is fourth after 12 rounds.

"There were some flat patches, probably around the investigation when players' interviews were being conducted.

"We could only lean on each other and we spoke on numerous occasions that the only people who knew what we were going through were the other people sitting next to you.

"That solidarity has held us in good stead so far."