I have seen many comments about the play of a center that decry the horrible job that they are doing, but the evidence given leads me to believe that the average fan has no idea what a center is supposed to be doing.
Pass Blocking assignment for a Center
If you are playing against a 4-3 defense there are 3 ways that a Defense can set up from a center’s perspective.
Number one is RUN STOPPER set-up. This is when the two defensive tackles line up in the 1a and 1 b positions. (The 1 position is the spot between the center and guard, 1a is between the left guard and the center and 1b is between the right guard and center.) When the two defensive tackle occupy the 1a and 1b positions at the snap of the ball the two guards are supposed to take a power slide step, with their inside foot (the one next to the center) toward the center, which moves their body into the slot before the defensive tackle can engage them. The center is supposed to snap the ball and immediately bring both hands up and forward, engaging both tackles at the same time. If either of the DT’s is beating the guard into the slot, the center is supposed to turn toward that DT and leave the other DT to be handled solo by the other guard.
Number two is MID-DOWN HYBRID. This is when one DT sets up in the 1 position and the other DT sets up in the 3 position (this is the spot between the guard and the tackle. This formation allows the defense to match a power right or power left formation of the offense, which is when the tight end or full back lines up on one end of the line. In this formation the center, snaps the ball and immediately turns to engage the DT in the 1 position while keeping an eye out for a blitz coming up the other 1 position.
Number three is BLITZ. This is when one DT sets up in the 3a position between the left tackle and left guard, and the other DT sets up in the 3b position between the right tackle and right guard. In this formation the defense likes to run two blitzers up the middle, say a linebacker and a safety, or maybe a defensive end will run a curl stunt. The center must snap the ball and stay put, looking for the blitzers picking up the first one to reach him. The second blitzer is the responsibility of the running back.
If you are playing against a 3-4 defense there are only 2 ways for a defense to set up. The Nose Tackle lines up in the 1a or the 1b position. In this set up the center has just 2 duties, number one is to double team with the guard on the NT… number two is to look for the stunt/linebacker/safety blitz and try to get one hand on them to slow them down.
If you are playing against a nickel package there are only 2 down linemen. In this defensive set, there are only 2 ways to line up again. The most common set up is for the 2 down linemen to set up in the 3a and 3b positions, with the blitz coming from the outside. This is designed to leave the extra lineman, the center, all alone while you overload one side or the other on the outside. When the center snaps the ball his only job is to look for a surprise blitzer coming up the middle. The second set up is to have the two down linemen lined up in the 1a and 1b position, with the blitz coming up the middle from the linebacker of the safety. This is designed to overload the middle of the line and leave the two offensive tackles out of the play. This is usually done when the offense is in a 4 receiver set and has an empty backfield. When the ball is snapped the center has to engage the two down linemen and attempt to stay square with the line of scrimmage. Both guards need to be engaged in double teams of the down linemen, the blitzer looks to see if the center gets turned to one side or the other and hits the gap on the centers back side that gets created from this turn.
Run blocking assignment for a Center.
This is the same for pass blocking, with the exception that on plays when the guard pulls, the center picks up the defensive lineman that was lined up in the 1 or 3 positions, and occasionally the center is the one that pulls instead of the guard. The other difference is that when the center assists the guard with his primary block, the center determines if the guard is getting beat or not. If the guard is not getting beat, the center performs a chip block and releases to the second level to pick up a blitzer or linebacker. If things are going really well then he may continue on to the third level block. The other difference is in the way that they block. For pass blocking the center wants to hold his ground, whereas in run blocking the center wants to drive his target backwards or redirect them away from the run.
The center has the duty to call out the defensive alignment before the snap. This is when you see the center pointing his finger and yelling out the blocking assignment to the other linemen. Really all he is doing is saying hey guys see that linebacker…he is standing right there. Look at that safety creeping up into the second level. Then he calls out the code for the blocking assignments for that particular defensive alignment.
Every time that you see a center one on one with a down lineman in a passing situation that means that one of the guards got beat or missed his assignment completely. It is a misunderstanding that the center is ever assigned to block a down lineman in the passing game. The center is only supposed to assist the guards and pick up the blitzers. This role as a blocking assistant is why you see teams moving a good lineman into the center position to extend the end of their career.