Everything wasn't always peaches and cream between Najee Harris and Nick Saban at Alabama ... the former Tide star just revealed he and his former coach used to fight each other all the time during his four years at the school.
The Pittsburgh Steelers star broke it all down on "The Pivot" podcast Tuesday ... saying Saban belittled him often -- and he would push back every time he felt the head coach went too far.
"I'm not the type of dude to sit back and just let somebody talk to me in a way and expect me not to say something," Harris said during the interview with Ryan Clark, Channing Crowder and Fred Taylor.