The NFL's new helmet rule will make it a 15-yard penalty for a player to initiate contact with the crown of his helmet.
The rule only includes tackle attempts made outside the tackle box. Incidental contact, which could be seen as a gray area, won't draw a flag
Still, it's a regulation that will have a drastic effect on many of the league's best running backs. It may be a throw-first league, but plenty of throwback players have utilized bulldozing running methods.
Let's take a look at the running backs who'll be most affected by this new rule.