A second sample is being looked at at present and if positive, the 'Premier Division' player will face a possible two-year ban from the game.
This would be the first case of a positive drug test in the eircom League, as anti-doping measures were introduced just over twelve months ago.
The drug would not necessarily have to be performance-enhancing - recreational drugs (i.e, cannabis) are also prohibited under the listing of banned substances.
Tongues are wagging as to who the player is, with many fingers pointing a number of possibles at the top Dublin clubs.