More trouble for Aldon Smith ... who was detained by police in San Francisco around 8 AM Thursday after a car he was riding in smashed into a cop car and the officer says Smith was drunk at the time.
The troubled Oakland Raiders star was NOT driving the car at the time of the crash, however cops did arrest the driver for DUI.
The bigger issue for Smith ... the alcohol allegations.
The 27-year-old has struggled with substance abuse and is currently serving an NFL suspension for violating the league's substance abuse policy.
According to reports, he's still in the league's substance abuse program -- we're making calls to figure out his status.
Smith is still in jail and cops say he'll be released when he sobers up.