Baseball in general had a massive cocaine problem in the 1980's, headlined by Steve Howe and his seven or so lifetime suspensions, as well as the 4 members of the KC Royals (Willie Wilson, Willie Aikens, Vida Blue and Jerry Martin) spending their off-season in prison on possession charges. The decade ended with famous Pittsburgh Drug Trials, where numerous players testified about their on-field and in-game use of cocaine,most memeorable of whom was Tim Raines, who testified in court that he used to slide into second base head first so as not to break vials of cocaine he had in his back pocket.
It was after this that baseball started instituting their drug policies, which were to root out cocaine originally, but included all illegal drugs.
And that was what evolved into today's steroid policies...