This is a topic that comes at a depressive state for most, but needed information as well. We always can think of players who have had their greatness cut down by injury. Examples would be: Grant Hill, Anfernee Hardaway, Sam Bowie and most relevant today in Greg Oden. There however, is the other side, in which the mental aspects of life, not the physical have hampered a player from greatness.
The NBA Drug Act was implemented in 1983 to try and deal with the rampant Cocaine use that had taken over much of the players in the association. That can almost be said for the large amount of players that use Marijuana in today's game was similar to the use of blow back in the late 70's and 80's.
With Udonis Haslem being recently indicted for an overblown Marijuana use charge, it brings about a common occurrence in the league's past.
The players specified here on the list aren't going to make the Top 5 list of All-Time players, that wouldn't be reasonable. These are guys who, because of some form of drug addiction, saw their careers fall apart. All five of them had great talent and for a period of time showed it on the court. They had the potential to have Hall of Fame careers, but just couldn't bring it all together.
There can be other players argued for on this list, but I felt these five had the most talent at their position.