BenSkywalker
Regular
When the frontline is trying to stop all those going for the ball, what's legal for them ? And the people going for the ball ? They can't tackle them obviously ?
Almost anything you can do without needing hands. Smashing helmets, shoving, dropping down and taking out someone's legs, all legal. You can't hit someone from behind who does't have the ball, and you can't grab a hold of people using your hands.
How do you get broken nose, if you are wearing helmet ? a Headbutt ?
Butting heads in the NFL is actually likely equally common to running. Half your positions are ones that mainly run around, the other half are on the line butting heads.
That's nasty. They should just play Ice Hockey.
In terms of being nasty, I think the NFL easily holds its own with the NHL(which is considerably more brutal then international rules hockey).
You can go for the neck ?
If you make it obvious, no, you can't go for the neck('clotheslining was banned sometime in the last couple of decades, it did used to be legal). However, most of the time people get slammed down from over someone's head they are in the air first, and get grabbed around the waist and slammed. Quite a few guys in the NFL have a vertical leap of 38"+(some over 40", over a meter for those outside the US), that puts them in a position where it is fairly easy to pull of an overhead slam.