Way back in the day you could take the head off a defenseless receiver, take a guy out with a spear, or go for the QBs knees (yes, that is illegal), or just crush him into the ground and win the locker room ante.
Deacon Jones' forearm shiver to the helmet --> Williamson/Plank --> Denver's chop blocking line --> Vontaze Burfict, with a lot of other stuff in between. I bet most people reading this don't even know what I'm saying with that, but the roughing rule and the helmet contact rule are only the latest in a long progression of rule changes to take violent (and often wilfull) injuries out of the game. Now, the QB has simply become too central to the game and too expensive.
With each step the defenders adjusted and nobody remembers how it was when "men were men". We still have Williams running over guys, so that's something worth watching in this game.
The yards and points keep inching up over the deades if not in a stright line as a result. I'm guessing that makes fantasy football more interesting.