Essendon's doctor Bruce Reid protested the "ludicrous" use of drugs at the centre of his AFL club's supplements scandal.
Dr Reid wrote a letter to coach James Hird and former football manager Paul Hamilton, saying drugs were given to players without his knowledge.
The letter, written in January last year, was initially thought to have gone missing.
But it was included in the AFL's statement of grounds, released on Wednesday, for the charges laid against Essendon officials including Dr Reid and Hird.
"It is my belief in AFL that we should be winning flags by keeping a drug free culture," Dr Reid wrote.
"It is all very well to say this is not banned and that is not banned but for example, the injection that we have given our players subcutaneously was a drug called AOD/9604 ... this drug is derived from the growth hormone.
"It is at the moment used for fat metabolism but also bone strength in children and may have some side effects that may be beneficial in bone growth.
"This to me just seems ludicrous at this stage where the only trials I have got are on how to lost (sic) weight and fat around the abdomen.
"... We are playing at the edge and this will read extremely badly in the press for our club.
"And for the benefits and also for side effects that are not known in the long term, I have trouble with all these drugs."
Dr Reid was uncertain at the time whether AOD/9604 was approved by Australian drug authorities.
He also cautioned against using the drug Actovegin to aid recovery of players.
"We are claiming that we should use it as a recovery agent," he wrote.
"To me it seems ludicrous that a few mls (millilitres) of calfs blood spun down is going to give you a concentration of growth factors and other factors that would speed up recovery."
Dr Reid said he was sure sports scientist Steve Dank believed the supplements program was ethical and legal.
"However, one wonders whether if you take a long stance and look at this from a distance, whether you would want your children being injected with a derivative hormone that is not free to the community and whether calf's blood, that has been used for many years and is still doubted by most doctors, is worth pursuing," he wrote.