In tomorrow's Herald Roy Masters reveals all on Andrew Johns's drug use.

Newcastle club doctor Neil Halpin joined Herald columnist and former coach Roy Masters by saying he too has long known former Australian captain Andrew Johns was a drug taker.

Halpin admitted to knowing of Andrew Johns' drug use for five years.

In a stunning admission, the first from a Newcastle official since Johns claimed the club knew of his behaviour last night, Halpin said he had been helping treat the player for some time over his alcohol, drug and health issues.

Andrew Johns admitted on television last night to longstanding drug and alcohol use,'' Halpin said in a statement.

"I have been aware of this since 2002.

"I have treated Andrew for many years not only for his football injuries but I have coordinated the management of his drug and alcohol abuse."

"I have personally spent many hours with him assisting him as far as possible with this and related issues.

"His abuse has related to so-called recreational drugs and there is no evidence whatsoever that he has ever used any performance-enhancing substances.''

Masters said earlier today he was not at all surprised by Johns' admission yesterday that he had taken drugs throughout his stellar rugby league career.

"It's been well known in the league community for a long period of time that Andrew Johns was a drug taker,'' Mr Masters told Southern Cross Broadcasting.

"I've confronted him with it, confronted his manager with it, defamation laws prevent you from writing it.''

Masters said Johns, who was also Newcastle Knights captain and is currently on leave from the club, where he has worked as a coaching consultant since his retirement with a neck injury in April, could have been one of the game's greatest coaches if not for his off-field problems.

"In my mind he was the greatest, because he basically could do everything - he was also a splendid thinker on the field, a great tactician,'' he said.

"He could have moved into a position of being one of the game's great coaches, however he's always had that problem with respect of his off-field activities, where he would have sent poor disciplinary messages as a coach that he could not have actually ever assumed that role in my mind.''

Masters said Johns had always used his "legendary humour'' to distract people away from the drug issue and onto his problems with depression.

"This is the great cycle that drug takers get on,'' he said.

"They go on a drug binge, they come out of it and they go back on it again in order to relieve the symptoms. It's a massive problem in society and one that the AFL is just starting to wake up to, whereas rugby league has known it's had this problem for about  10 years.''

AAP