49ers 2017 Season: San Francisco’s new pass defense

The scheme

When you look at the basic Xs and Os of what the 4-3 under is, you find a base defense designed up front to use strict gap control and allowing the front seven to come off the ball quickly without having to guess which side of their blocker the play is going to.

The scheme is designed to promote extra run control and pass rush with speed off of the snap and simplicity in responsibilities because of extra men along the line of scrimmage who have fewer duties than normal base fronts.

This, in turn, causes double duties for the dedicated pass defenders that would normally be in a simple man or zone coverage. They must now disrupt the routes of the main wide receivers on the outside with press if they are corners, or cover more of the field in support of the pass as safeties, all while backing up the run defense; this is just the base concept.

This is compensated by the elevated pass rush that is generated by the quick get-off at the line of scrimmage and the dedicated pass rush of the LEO or “Elephant” position or any stunts that might be used to mix it up by the front seven.

When interior lineman are not required to hold up their blocks and play both sides of the blocker, they then can shoot through their designated gaps like mad men and blow up plays.

To be specific at every position out of the base front, it works like this:

Defensive Tackles

The strong-side DT is basically a nose guard. He can be short and stout but needs to be able to eat up blocks and be good at playing the run because he will often be double teamed.

The weak-side DT should be good at playing the run but also be a very adept pass-rusher from the inside.

Defensive Ends

The strong side DE is your best run-stopping DE, he should be able to control the strong-side C-gap between the guard and tackle and eat up blocks as well.

The weak side DE is the heralded “Elephant” or LEO. He will be a dedicated pass-rusher with the added responsibility of containing any rush that attempts to scoot around the outside of the weak-side offensive tackle. Primarily he is pressuring the quarterback and might have help on the outside from his supporting cast.

Linebackers

The SAM LB is going to play the strong side of the play outside the tight end and not only watches the D-gap for outside runs but, most importantly, must be able to run with the TE and cover him on pass routes. Often he might run stunts to pressure the QB or peel out to cover the strong-side flats if need be. This is a tough position.

The MIKE LB has strong side B-gap responsibility and stuffs the run there. He is also responsible for dropping back into coverage in the different variations of this from. Most importantly the MIKE is the captain of the ship when it comes to the front seven. He will call the assignments and audibles after he reads what is happening on the offensive side of the ball.

The WILL LB is responsible for the weak side A-gap before all else. But with his limited pass-coverage responsibilities, he often bats clean up on the run across the board.

This player quite often registers a lot of tackles out of this front:

Safeties

There is a lot of talk about the difference between the strong safety and the free safety when it comes to personnel and their measurables. Typically they have distinguishing characteristics. After much research and scheme specific ideology, I honestly have to say that these two positions need to be interchangeable in the 4-3 under system.

Depending on how the offense lines up in this system, either one could be responsible for more run support or man coverage that puts them closer to the line of scrimmage or playing the deep field in support of the corners on pass routes.

This might not be a popular opinion. But with all the variations of this defense and all its possible coverages, I believe it to be true.

Corners

Historically, both corners need to be physical in order to disrupt the pass routes off of the snap. In addition, they also need to be excellent pass defenders in their ability to break up the reception with the ability to play man to man and run with WRs.

Many would say that a tall and long body type is best for this position and they should possess a natural tackling ability. I personally believe that most of this is true. But the most important things are the ability to jam at the line of scrimmage, run with receivers and break up receptions.

Breakdown

What the overall scheme breaks down to is an advantage against the run and QB pressure. The 49ers were absolutely horrible at both last year, and the advent of this new scheme attempts to address those weaknesses.

If there is a need to fully break down the nuts and bolts of this defense, Danny Kelly of FieldGulls.com wrote a series of articles in 2011 that were excellent.

The next step in fully understanding what San Francisco’s pass defense will look like this year is analyzing the players that we now have at our disposal and how they will be used.