No, the The Basketball Diaries is not a sports film but an urban drama based on New Yorker Jim Carroll's autobiographical writings about his youthful descent into heroin addiction. Although sometimes stylistically predictable in tracking the transformation of a group of high-spirited working class school kids into societal dregs, the film manages to convey the wretchedness of the life of street junkies with great effectiveness. This largely due to Leonardo DiCaprio who is outstanding in the central role, one that was originally intended for River Phoenix who died in October 1993 of drug-induced heart failure. The film also features an early screen appearance for Mark Wahlberg.
FYI: If you are interested in a similar subject matter given less conventional form check out Darren Aronofsky's Requiem For A Dream (2000).