Less ominous, but still worthy of concern, might be the potential increase of injuries to the ribs, legs, knees and, in fact, the entire anatomy below the neck that will now be the legal target area for defenders.

One thing is certain. If officials and players abide by this new rule, the art, science and brutality of running and tackling will change in some respects and, like everything else, the game will evolve. But based on the NFL's history of great runners, players will just find another way to get the job done.