Cam Newton just delivered an impassioned speech to Rashee Rice ... warning the Chiefs star that if he doesn't shape up soon -- his time in the NFL could be over in a flash.
The former Carolina Panthers quarterback sent the message loud and clear on his "4th&1 w/ Cam Newton" podcast this week ... going off on Rice for around five minutes over the recent decisions that have led to police investigations.
Newton advised the wide receiver to lay as low as possible going forward .