I love Kupp out on the edge, his ability to make someone miss and will himself to get a yard and a half is exceptional. I trust Kupp to get that first down every time. The problem is that the Colts blitzed Leonard right into Kupp's path and he didn't have a chance. It was a great call by the Colts and bad luck, but if the Colts don't blitz that player right into that gap the Rams likely get the first down and run out the game.
