A live war broke out between beloved R&B group Jagged Edge and NFL star Nick Fairley -- when the Saints star hijacked their concert ... and the singers told him to get his "big ass" off the stage.
It went down Feb. 24 at the Grand Marshal's Ball -- a Mardi Gras event in Fairley's hometown of Mobile, Alabama -- where Nick was the Grand Marshal and Jagged Edge was the featured entertainment.
But when JE took the stage, all hell broke loose because the 6'4", 300-pound defensive lineman refused to get off .