A former AFL rookie who took part in Essendon's catastrophic supplements program has spoken to the ABC in detail about his battle with the club to find out what exactly he was injected with.

Key points: Hal Hunter took part in supplements program during 2012 season

Hal Hunter took part in supplements program during 2012 season ASADA believes he may have been injected with an equine supplement

ASADA believes he may have been injected with an equine supplement He has taken Essendon to court in a bid to find out what he was given

He has taken Essendon to court in a bid to find out what he was given In response, Essendon has pursued Mr Hunter for legal costs

"They've been fairly disrespectful," Hal Hunter told Four Corners.

"They've treated me like I was the youngest player, I was a rookie, I wasn't important and I'm still not important. They're treating it like it's an issue that's just going to go away."

Mr Hunter was 18 when he was drafted by Essendon in December 2011, and took part in the program during the 2012 season.

He was delisted in September 2013, following a series of injuries, and now no longer plays football.

In 2014 he approached the club, requesting details of the supplements he was given and the injections he received, but Essendon refused to tell him.

"There's been lots and lots of delays. They seriously questioned why I needed them, what my motives were. They claimed I was a disgruntled ex-employee," Mr Hunter said.

"They've tried to brush me off, like I'm not important. It's been almost a year-and-a-half and I still don't have any answers to the questions I'm asking. And I'm no closer to finding out what I was given."

After Mr Hunter and his legal team gave notice to Essendon and the AFL that they were considering launching legal action, the club produced Mr Hunter's medical records in June 2015, followed two months later by incomplete records of some of the supplements he had been given.

Last week, having previously assured a judge they had handed over all the documents in their possession relating to Hunter, the club produced a further set of documents.

But these shed no light on what exactly he was injected with.

Mr Hunter's father James told Four Corners it is an "appalling situation".

"Hal's simply trying to understand what the club allowed to happen to him whilst he was in their care and he's been forced down a road that he really shouldn't have had to go down," he said.

Supplement labelled 'for equine use only'

Mr Hunter knows some of the pills he was given at the club, but has no idea what he was injected with off-site, at a Melbourne clinic called HyperMED.

As revealed on Four Corners tonight, the Australian Sports Anti-Doping Authority (ASADA) believes he may have been injected with an equine supplement, without having given formal consent for this to happen.

"My understanding is that according to the evidence of one of the players, they had at some point seen a label on a jar which said: 'for equine use only'," ASADA CEO Ben McDevitt said.

The supplement in question was brought into Australia from overseas by a patient of Melbourne doctor Robin Willcourt.

"The person concerned picked up this concoction, if you will, of amino acids with vitamin B in it and that's used in lots of detox programs. There's nothing bizarre and strange about that," he said.

But Mr Hunter's mother, public health microbiologist Melita Stevens, disagreed.

"It's of course highly unethical to inject somebody with somebody else's medicine and to not have the appropriate controls in place or the forms or the provenance of those compounds," she said.

Sorry, this video has expired Hal Hunter speaks to Four Corners

Mr Hunter has gone to court to try and force the club to hand over all its documents relating to the supplements and injections he was given.

In response, Essendon Football Club has pursued Mr Hunter for costs. The club's strategy has shocked and angered Mr Hunter, his family and his legal team.

"I think everyone can identify with what's happened to the Hunters in this case," said Mr Hunter's lawyer Patrick Keyzer.

"Imagine if your child was injected with all this stuff and not only do they not know what it is, they're not even willing to tell him.

"They're not even willing to tell him that they don't know, and now, trying to make him pay for the privilege of finding out. It's shocking."

'Grubby and petty' legal fight

Ms Stevens told Four Corners it shows "the club actually doesn't care about the players".

"They are setting an example. They're using Hal to say 'don't fight us, we're going to fight you every step of the way'. And it's grubby and it's petty that they have gone after a 22-year-old boy to pay their costs."

Family lawyer Jim Constantinou commented: "To say that an employer should have the employee pay legal costs of the employer in circumstances where the employee is seeking to ascertain what he was ingested with and what documents are in existence to prove or disprove that, is beyond belief."

Essendon Football Club has not yet responded to a series of questions from Four Corners sent last week, but the AFL has issued a statement on the matter.

"The AFL investigated and prosecuted the Essendon Football Club for the program at the club in 2012, including imposing historic fines and penalties on the club," it said.

"The majority of the players involved are still in legal proceedings with the Court of Arbitration for Sport, under the advice and support of the AFL Players Association.

"However, the AFL is fully aware of the responsibilities of the game, and the duty of care owed to the players.

"The AFL is in discussions with representatives of individual players and groups of players about the impacts of the program in 2012.

"The AFL will ensure that the Essendon Football Club delivers on its responsibility to players, and will ensure that the medical protocol agreed to by the Players Association and the football club is fully delivered."