Jason Kelce's rivalry with the Cowboys is still going strong even in retirement ... check out the barb he threw Dallas' way Monday night -- it was so fierce, even his ESPN colleagues winced!!
The jab went down just before the Cowboys kicked off their "Monday Night Football" matchup with the Bengals ... as Kelce and the rest of the "Monday Night Countdown" crew were previewing the game live from AT&T Stadium.
Scott Van Pelt was attempting to switch segments from ESPN's "The Simpsons" coverage back to live action -- when he informed the audience of where they were located.