Manchester United manager Sir Alex Ferguson has vowed to sack any of his players caught taking drugs.
Ferguson has stood by United defender Rio Ferdinand, who has been the centre of a drugs controversy after his failure to take a test.
But the manager, whose side crashed to a 3-1 home defeat to Fulham on Saturday, said he would not tolerate any players taking drugs.
"If there were any danger of one of our players dabbling in any kind of drug, be it to enhance his performance or for his social life, he would be quickly gone from Manchester United," he told the News of the World.
"Be assured that the manager, his coaches and medical staff would know. Believe me, we have nothing like that at Old Trafford."
There has been no suggestion that Ferdinand has been taking banned substances, but his failure to take an official test is a serious matter and could lead to a lengthy ban.
The Football Association has gathered evidence surrounding Ferdinand's missed test and is considering its course of action.