The Packers and Lions got heated before the football was kicked off on Thursday Night Football ... 'cause head coach Matt LaFleur mixed it up with a fan pregame, and the altercation was captured by TV cameras!
The clip starts with LaFleur jawing at a Detriot Lions fan, wearing a Brian Branch jersey, on the Ford Field gridiron ... appearing to yell something along the lines of, "Shut the f*** up," as he walked towards the guy,
LaFleur's players, including Jayden Reed, followed behind their coach .