In the previous writeup, we described how zone blocking works by showing you a simple dive play with dumb defensive lineman and how, in theory, to block the run perfectly. Of course, only the Raiders have defensive linemen like that. (Low blow, I know, but come on -- they are the Raiders. By the way, thanks for Palmer.) The reality is that these men move and blitz and make plays.
In a perfect world, our Arizona Cardinals would block perfectly every single time and have no problems and get six ards every single running play. Wouldn't that be nice? But the only players to record six yards per carry over a single season and and are not in jail are Eric Dickerson and Barry Sanders. (O.J. Simpson did it toom but doesn't fit my criteria in this case). So why doesn't it work like that? It is mainly because the defense does its job and makes plays. So this is where the cutback comes into play.
Let's say the nose tackle feels the outside pressure from the center and does what he is suppose to, which is drive against it toward the press and not allow the guard to get a wall. This now means that the weak side linebacker is going to have a free shot on the ball carrier because there is no one there to block him. This is very true... so naturally we're screwed right?
If the center can't get off the block, he will know this and his new job will be to stay on his block and drive him whichever way the lineman is going, effectively putting him right in the hole for no gain. Now the guard that was supposed to take over that block is just standing there with his thumb up his butt...not really. His job and part of the reason his first step is to the right is to allow for the cutback lane. The weak side linebacker is going to flow towards the ball and can overcommit.
Look at the size of this hole! My mother can run through that hole with a tractor trailer and not get touched for 15 yards. Now this is why the vision of the running back is so important. If he is Eric Metcalf (props to people who get these references, i was there too), he dances around a lot he is going to get stopped for no gain. But if he sees the field properly and makes his one cut, he is going to be running for 10 yards. He comes right off the center's butt and now is in the open field, where he can make a safety miss and you go all the way.
Here is Brian Billick going more into detail about the cutback lane that is formed when a defense overpursues a zone blocking team. Also, if you look closely, you can see instances of everything I have been talking about for three writeups now -- double teams, combo blocks, etc. Let me know in comments what you want my next write up to be about. I'd love the ideas.