Former NBA 1st round draft pick Isaiah “J.R.” Rider was arrested in Arizona this week for violating his probation … TMZ has learned.

Rider — who played in the NBA from 1993 to 2001 — is currently behind bars in Maricopa County on a no-bail hold.  It’s unclear why police believe Rider violated his probation.

Rider’s probation stems from a 2010 incident — where he fled from police after they tried to pull him over for driving erratically. He pled guilty to unlawful flight from a law enforcement vehicle.

– Reported by TMZ.