Base Rules for a 4-3 Defense
The 4-3 defense is a great defense for any level. By using four defensive linemen and having each of these linemen responsible for a gap the linebackers can play downhill and control the box. In this article we will look at the alignment of the base 4-3 and the responsibilities of each position group.
The Defensive line
In the 4-3 it’s critical that the defensive line is able to control their gap. The defense is based on each lineman being responsible for one gap and controlling that gap. In the 4-3 there are four linemen each with a specific alignment and role.
Diagram of D Linemen vs. 1 TE Set
The linemen will pick the strength based on the Tight End. This will dictate their alignment and create a strong side and a weak side. On the strong side of the line there will be the Tackle and the Strong End. The Tackle will align on the outside shoulder of the Strong side Guard. He is responsible for controlling the B gap. The Strong End will align on the outside shoulder of the Strong side Tackle. He is responsible for controlling the C gap. If there is a Tight End he can move his alignment to the inside shoulder of the Tight End but is still responsible for the C gap.
On the backside of the formation the Nose and Weak End are responsible for shutting down the A and C gaps. The Nose will align in a Shade technique on the Center. This means that he will set up on the weak side shoulder of the Center and control the backside A gap. The weak side end will be responsible for the C gap. If there is a second Tight End added to the formation he will get help on his outside so he can keep his focus on the C gap.
The linebackers are the strength of the 4-3. This defense is built to have players that can make plays and adjust to the stop the offense. There are three linebackers Sam, Mike and Will. Each of these has a specific role.
The two linebackers who have the most responsibility in stopping the run are the Mike and Will linebackers. The Mike or Middle Linebacker is responsible for the strong side A gap. This must be a player who is willing to come downhill, take on a block and make the tackle. The Will or weak linebacker has one of the toughest jobs in the defense. He is responsible for the backside B gap. This is a favorite gap for offenses to attack so the Will must be able to stop any run threat inside to the B gap and also must be able to scrape outside to help the Weak End on any outside run.
Responsibilities vs. Iso
Strong Iso (to TE side)
Weak Iso (opposite of TE)
When there is any running play with a lead blocker the linebackers must work together to stop the run. If the offense runs an Iso to the Strong A gap the Mike must come up and take on the blocker while keeping his outside shoulder free. The Will should help him out by scraping over and filling inside of the lead block to make the tackle. If the offense runs a lead play at the weak side they will switch roles and the Will linebacker will take on the blocker while the Mike scrapes over to make the tackle.
Diagram of Sam Alignment vs. Spread
The third linebacker, the Sam, is what makes the 4-3 unique. In the 4-3 the Sam does not have a specific gap inside the box. This allows him to be the D gap defender so he can force any outside run in. He can also play any 2 WR sets to the strong side which is very useful as more offenses go to Spread sets. If there is a Tight End the Sam will come down and align on the Tight End’s outside shoulder. This lets the Strong End stay C gap responsible while still accounting for the extra gap.
The 4-3 Secondary can take many different forms. Just like most secondary units it consists of two safeties and two cornerbacks. The safeties are designated as either Strong (to the Sam linebacker) or Free while most of the time Cornerbacks are responsible for given sides.
Cover 2 Responsibilities
The weak side secondary has to find a way to get an extra defender to help the Weak End stop the outside run. There are multiple ways of doing this. Some teams will go with a Cover 2 look where the Cornerback is now responsible for any D gap run and the Safety plays over the top.
In cover 2, the Cornerbacks will be contain players on run support, safeties stay deep half.
Cover 4 Responsibilities
If the defense wants to get the Safety more involved in the run they would go with a Cover 4. In this coverage the Safety is responsible for the D gap and the Cornerback has the Deep Quarter.
In cover 4, the safeties have contain on run support and the cornerbacks play deep.
Cover 3 Responsibilities
The third way defenses can cover add a secondary player to the box is by running cover 3. In this coverage the Free Safety can come down to linebacker level just outside of the Weak End. This adds a defender against the run and can be an effective way to deal with a Tight End to the weak side.
(See Also) Cover 4 Zone- Pattern Reading Concepts
(See Also) Understanding Cover 2 Zone
(See Also) Zone Blitz- 4-3 Defense