Three Wests Tigers rugby league players - including their captain, Robbie Farah - were photographed at training using their secret weapon in the race to the finals: masks to inhale an artificial oxygen mixture to help recover from injury.
But the practice, viewed by the World Anti-Doping Agency as ethically wrong, is under review and could be banned by the end of the year.
The Australian Sports Anti-Doping Authority said it was not concerned at the use of the oxygen mixture by Farah and the injured forwards John Skandalis and Keith Galloway, a view shared by the National Rugby League.
The authority's chairman, Richard Ings, said he believed there had not been a case prosecuted anywhere in the world over oxygen mixtures.
Under the world anti-doping code, ''the method of artificially enhancing the uptake, transport or delivery of oxygen is banned''.
An NRL spokesman, John Brady, said the Wests Tigers and Manly used a technique known as hypo-oxygenation - diluting the amount of oxygen - which he believed was not covered by the rules. He said world anti-doping rules applied to increasing oxygen, not decreasing it, although he said there could be changes next year.
Hypo-oxygenation makes the body use smaller amounts of oxygen more efficiently by increasing the number of red blood cells. The technique creates a physiological effect similar to altitude training.
The Wests Tigers chief executive, Stephen Humphreys, said: ''The NRL is extremely competitive and we are a highly professional club, always looking to enhance performance, but always within the rules and spirit of the game.
''If in time this is proved to be illegal then of course we will discontinue it.''
The club's high performance manager, Cherry Mescia, would not give details of the regime but said: ''It is a different form of training we have at Wests Tigers. We don't want other clubs knowing what we do''.
Yesterday the Tigers trio looked like spacemen, breathing through their oxygen masks and holding canisters as they slowly paced along the boundary line at Concord Oval.
The players have been using the treatment since the pre-season to aid recovery from injury. Galloway has had a persistent knee injury, Skandalis a corked leg and a bruised Farah came off the field 20 minutes before full-time last Sunday.
The Wests Tigers have been using the masks and oxygen system regularly before scheduled training.
It is not only the NRL treatments involving manipulation of oxygen that are under the spotlight.
This year the Carlton Australian Rules forward Brendan Fevola wore a ''moon helmet'' and a breathing mask and spent four, two-hour sessions in a hyperbaric chamber in a bid to help the healing of his bruised heel.
All AFL clubs use these chambers - more commonly known for their use in treating divers with the bends - because breathing an atmosphere of 100 per cent oxygen is believed to improve healing, reduce swelling and stimulate blood vessel growth.
Collingwood has its own ''altitude room'' - a $100,000, 60-square-metre exercise chamber which simulates the oxygen-depleted air of altitudes up to 3000 metres above sea level.
