David Arquette -- Pick-Up Basketball Game Becomes Rehab Picker-Upper

David Arquette SCHOOLED a bunch of rehabbers in L.A. this week ... in more ways than one -- showing off his filthy skills on the basketball court ... then teaching them a thing or two about staying sober.

Sources tell TMZ, several inpatients from a place called Chabad Residential Treatment Center hit up Pan Pacific Park Tuesday for a pick-up basketball game -- but when they arrived, they realized they were short one player.

According to sources, Arquette was standing nearby at the time and noticed they needed a fill-in -- so he offered up his services.

Needless to say, Arquette -- who's famously nasty on the court -- mopped up with his team, who then informed him they were from the local rehab center.