You mean the tackle that was actually carded and punished? We see borderline red tackles every game. Sometimes its a red, sometimes they aren't, and sometimes they make a mistake. Havertz' one wasn't the only tackle that gameweek that could have been given a red but wasn't. The point is that while I could understand a red being given, a yellow for it is not anywhere near as massive a blunder as not sending off a player for deliberately striking an opponent in the back of the head.