Originally Posted by Deadspin

A chop block is a thigh-or-lower block on a defender who is already engaged with another offensive lineman. (Chop blocks and cut blocks are not the same thing. A cut block, which is legal, is a below-the-waist block involving only one defender.) Guard Pat McQuistan, as you can see in the video above, blocks Aldon Smith at the waist. That's not a foul, just good offensive line play. Only if McQuistan had hit Smith in the thigh or lower—even if Smith was not physically engaged with tackle Breno Giacomini but preparing to rush him—would the flag have been justified. Blockers never can go high-low on a defender on pass or kicking plays.

But not all chop blocks are illegal. On running plays, offensive linemen can go high-low. The NFL rulebook gives three such situations. Two offensive linemen who had lined up next to each other on the line of scrimmage may chop a player whenever they'd like. Two offensive linemen who had lined up with one or more linemen between them—e.g., a center and a tackle—can chop a player, too, so long as the play is moving toward the block. For instance, a right tackle and a center can chop a defensive end on a run to the right, but not on a run to the left. Backs can chop in concert with linemen, too, so long as the block takes place outside the tackle box.

The NFL's reasoning behind all these proscriptions is that defensive linemen are much more likely to be injured on low blocks when they can't see them coming. On a run-stopping rush, the thinking goes, defenders are eating up space, preparing to make tackles, and following the flow of the play: they're more likely to be aware of what awaits them, especially if it comes from two adjacent linemen. In pass-rushing situations, there's no flow to the play, and defenders are running hard at one (mostly stationary) target. A chop block surely would catch a pass rusher off-guard.

Originally Posted by ForThoseAboutToRock

Do teams "script" their opening offensive series? If so, why?

If there is such a thing as a script, is it sort of open ended and branched, or is it a pretty strict thing, almost regardless of down and distance?

If it's a good idea to script the opening drive, then why is it not a good idea to script multiple drives, if the defense is acting as you expected them too?

Finally, does anyone have an idea on the BB/JMcD school of thought regarding scripted series?

Thanks for any insight on this.

Originally Posted by chicowalker

If the QB then makes a quick throw to that TE/WR/RB, what prevents the contact from turning into PI?

Originally Posted by rlcarr

Nothing. And it should be DPI. You can make contact in the first 5 yards, but that only means no illegal contact should be called. But once the pass is released, it's hands-off time or else DPI.

Originally Posted by chicowalker

Right, but what I'm saying is if it's a short / quick pass. Practically speaking there might not be time to disengage.

Originally Posted by chicowalker

Right, but what I'm saying is if it's a short / quick pass. Practically speaking there might not be time to disengage.

Originally Posted by DocHoliday

That's why it's so important the defender turn his head!

Also the QB usually will not throw at a receiver being engaged heavily with a CB.