Thursday, July 12, 2012

4-3 Defense - Simple Basics

You may have read that the Denver Broncos use a 4-3 defensive alignment.  If you’re not familiar with defensive schemes, what in the world does this mean?  Allow me to simplify this terminology and explain the basics of this defensive alignment.  A 4-3 defense is defined as four defensive lineman on the line of scrimmage and three linebackers traditionally lined up behind the four linemen.  The following graphic should help explain this defensive scheme (Forgive the simplicity of the graphic).

Linebackers:                            W             M            S
Defensive Line:                     DE       DT       DT       DE
Line of Scrimmage:       ---------------------------------------------------
Offensive Line:                       OT       OG     C    OG      OT      TE
Quarterback:                                               QB
Fullback:                                                     FB
Running Back:                                             RB

Weak Side                |              Strong Side 

The overall concept of the 4-3 defense is to have four defensive lineman that the offense must always allocate how to block and defend on the line of scrimmage.  This alignment places those four linemen in positions who have the opportunity to make a play on the run or to force a sack or incompletion from the quarterback on passing downs.  If the defense has a proven threat either as a lineman that is prominent to sacks or a lineman that can defend the run, the offense must adjust their line or protection schemes to account for this defender.

A perfect example of the 4-3 defensive line and its possible dominance are the New York Giants.  The New York Giants defensive line can dictate how the offense lines up across the line of scrimmage because of their strong dominance in the pass rush from the four men up front.  Look at the previous two Super Bowl victories over the Patriots.  Each victory had four defensive linemen that the Patriots had to game plan round.  Because of the defensive line, Tom Brady couldn’t get a win in the Super Bowl this last February or in the 2007 season.  The “Great Equalizer”, as the New Your Giant’s line has been called in the past (the four defensive linemen), was able to reach Tom Brady and force sacks, incompletions, and interceptions without bringing a linebacker on a blitz.  This allowed the Giants to get pressure on Brady so he didn’t pick the defense apart and it allowed the Giants to drop 6 to 7 players into coverage thus allowing them to defend the pass.  With these extra defenders, they disrupted receivers more frequently and thus limiting Tom Brady and the Patriots on what they do best, throwing the ball to their play makers, wide receivers Randy Moss and Wes Welker in ’07 and tight end Rob Gronkowski and wide receiver Wes Welker in ’11.

What does a strong defensive line mean for the linebackers, the “3” in the 4-3 defense?  The linebackers play “gap” coverage on the run and either a man to man, a zone, or a combination of man and zone coverage in passing situations.  Gap coverage is when a linebacker, in simplistic terms, plugs the holes at the line of scrimmage that are opened up by the offensive line and tight end for a run by the fullback or running back.  If three linebackers are free to defend against the run, it increases the chances a stop near the line of scrimmage will occur.  If on a passing down the lineman are getting up field applying pressure on the quarterback, the linebacker can either play the “hot” route zone (the area where a primary receiver will run to when a blitz or quick pressure is anticipated on the quarterback) and wait for an interception or they can come free (not blocked) up field and blitz the quarterback for a sack.

Where the 4-3 defense can go wrong is if the defensive line cannot disrupt the quarterback or stop the run (obvious), thus causing a chain reaction through the defense.  Let’s dissect what this means.  With a non-dominant 4-3 defense, the offense can get away with only using the offensive lineman to block the defensive line because they don’t pose a threat to pressuring the quarterback, thus freeing the tight end (TE) to release from the line or chip block (quick block) and then release from the block to a passing route.  If the tight end is allowed to release off the line, then this tight end will need to be covered, either by a lineman, linebacker, or defensive back, typically a safety on the defensive side.  This causes match up problems when a tight end is a dynamic receiving threat.  Defenses usually don’t have a defender that can match the tight end’s athletic ability and thus is forced to either leave them open in man to man with this disadvantage or add double coverage help over the top with another linebacker or defensive back. 

To point out a few obvious issues, the defensive line can’t get to the quarterback and the tight end needs to be double covered.  That means the defense has 6 defenders (four on the line and two covering the tight end) occupied while there is still the obvious problems of getting to the quarterback and covering the remaining receivers running passing routes.  There are four remaining receivers, three wide outs/receivers and one running back that need to be covered.  Taking this into account, how does the defense get to the quarterback and cover the receivers with only five defenders remaining; one safety, one linebacker, and three cornerbacks?  The short answer against a good quarterback is…the defense can’t…they have to make a choice; commit to sacking the quarterback or commit to defending the pass because if they try to do both, it won’t be pretty.

The top quarterbacks will more than likely win against a defense that has to make this choice.  If the defense chooses to commit to the sack, the defense will usually get a few sacks at the beginning of the game (when this game plan is new to the opposing offense), but once the quarterback and opposing coaching staff diagnose what the defense is doing (applying the pressure but leaving holes in the defensive backfield), the sacks will stop and the passing yards will start adding up.  If the defense chooses to stop the pass, the offense will look for match-up problems on the defense for passing routes and commit to the run more than the original game plan thus forcing the defense to be uncomfortable either stopping the run with different personnel or alignments or stopping the pass with known match-up problems.

For the linebackers, this means that instead of sending a linebacker free off the line of scrimmage to blitz the quarterback, the linebacker is either busy in coverage double teaming a safety or being occupied and blocked on the line of scrimmage when he does blitz.  Thus is the defense wants to get any pressure on the quarterback at all, they may need to send two defensive personnel on a blitz, a linebacker and a defensive back and play man to man coverage in the backfield hoping the blitz gets the quarterback.

It’s not all hopeless for a defense like this to loose.  The best defensive coordinators, think Steve Spagnolo, Greg Williams, etc. can disguise coverages and take away half of the field to try and cause the offense to play “slow” (Playing slow indicates the offense is being forced to make decisions they haven’t practiced enough, or aren’t use to making) and thus put pressure on the quarterback to place the ball in the right place slower than what he’s like.  This disguise can work, but it takes an evil genius of a defensive coordinator to install this to make it work AND enough points on the board to support this defense with holes in it.  (See the Saints in 2009; not the most dominant defense with Sacks, but they took enough away from quarterbacks and disguised their intentions to create turnovers and give the ball to their high powered offense run by Quarterback Drew Breese and Head Coach Sean Payton.)

In summary, a 4-3 defense works well with the right personnel and scheme.  If the defensive line can occupy space and get to the quarterback without help, this will allow a linebacker or defensive back to come free on a blitz to sack the quarterback.  Getting to the quarterback for the 4-3 defense with just the defensive line through sheer determination and ability is the most important aspect of a 4-3.  That’s why the second or third highest paid position on a NFL team is the defensive end (DE) because that position is traditionally the position that gets to the quarterback and forces pressure from the defensive line. Then once the line can get to the quarterback, this will allow the defense to drop 6 to 7 personnel into coverage to defend the pass effectively by forcing the quarterback to hold onto the ball for an additional second looking for open receivers allowing the line to get there and get a crucial sack.

Go Broncos!


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