With the NFL execs voting 27-5 to outlaw the horse-collar tackle (a/k/a the Roy Williams rule) after a season where Williams alone caused three injuries with the move, I have mixed feelings on how this will work.
I do think it is good that this rule will help protect the health of the players, because when big-name players get hurt (like TO) I think it hurts the league. Had Philadelphia not made it to the Super Bowl and TO not had a chance to play, all offseason the Eagles would be talking about how that injury ruined their season (because for them, it was Super Bowl or bust!).
Granted, you are still allowed to use this move on a quarterback in the pocket or a tailback in the tackle box, but the severity of potential injury in those situations is not as great as in the open field, where a receiver would get caught from behind. Which leads me to my greivances about this decision.
How is a defensive back supposed to catch a speedy receiver from behind. If Randy Moss is streaking down the sideline with some spare DB having no chance to make a legitimate tackle, the "horse-collar" move is one of that defenders very limited options for a TD-saving tackle. While the defender could try to dive at the receiver's feet, hit them into each other, and hope he trips, if that offensive speedster stays up, it's six points.
The horse-collar move was good because it gave defenders a way to catch someone from behind and hold on to them to bring them down. Taking that away will lead to more break-away plays in the secondary.
Part of the ruling does say that the defender can't grab the collar and immediately pull them down by the collar, so if they hold on, is the tackle them legit? And if that is the case, why would a defender wait to pull an offensive player down when at the time he'd be giving up valuable yardage.
I think there is a simply way to deal with this rule. Fine a player who does it. Don't make it a 15-yard penalty, because if you do, the defenders will either (1) not make the tackle and give up big yards, or (2) use the horse-collar move to bring them down, which would end up giving the offense the yards anyway via a 15-yard penalty!
The defense can't win with this rule having an on-the-field effect, but if you fine a player who does it after the game, then it won't have a direct effect on the outcome of the game.
I know it sounds like I'm flip-flopping on this, but the truth is I can see a legit reasoning for and against this rule. I think the only real way to determine if this will be a success will be a season spent with this rule in effect on a trial basis.