The trenches are a violent place on the gridiron, pitting very large individuals against one another, snap after snap. There’s just two jobs at play: the offensive line preventing any defender from penetrating the pocket, and the defensive line doing everything in their power to get into the backfield. With the level of physical impact on every play from scrimmage, it’s near impossible for a player, offensive or defensive, to be on the field every time the ball is snapped. This makes the art of the defensive line substitution all the much more important. [LIMITED TIME: 50% OFF of annual member…