Tuesday, July 24, 2007

Football 102

Today's lesson focuses on defense.  Defenders have the luxury of being able to move before the snap, thus being able to change mathcups, or otherwise try and confuse the offense. And defenses are not limited by how many players must be at the line of scrimmage, or how many linebackers or defensive backs are on the field.
Typically, defensive coordinators like to think in terms of "conventional wisdom" and lineup in a 3-4 or a 4-3 (with 4 defensive backs) as their base defense.  But, sometimes innovation comes along.  Oklahoma used to run a 4-4 defense back in the day to try and get more guys up at the line against their power-rushing opponents.  And our old buddy Bill in New England has deployed a varying number of linebackers and defensive linemen in various circumstances.
When you hear them talking about "nickel" or "dime" packages, that refers to passing defenses.  When its a nickel, that means there are 5 (nickel, cute, huh?) defensive backs, and a linebacker comes out.  Often, the package means a pass-rushing specialist comes in along the defensive line.  When its a dime, it just means there's a 6th defensive back.  Funny that its called dime, because it doesn't have a clear history...Again, a linebacker comes out for this unit.
There are run defenses as well.  Typically, you'll have bigger players lined up along the line to try and occupy space.  And the safeties or corners may be replaced by a linebacker or bigger gentleman.
So, that's the general lineup, but how do they play defense?  Well, that depends on what they think the offense will do, and what history tells us about various situations.  For example, 3rd and short will almost always signal a running play, while 3rd and long will signal a passing play. 
Depending on the scheme the coordinator runs, he'll have his players lineup in certain positions and play a particular role. 
In a "conventional" 3-4, the lineman are noted as right defensive end, nose guard, and left defensive end.  The noseguard is lined up over center, and almost invariably his job is to occupy the center, though sometimes, he'll take an unusual angle and take up a guard as well.  His job is to disrupt the blocking if its a run play, or to collapse the passing "pocket" if its a pass.  The ends are used to take up the blockers on running plays or to try and get to the quarterback on passing plays.   But, its more intricate than that.  Sometimes, each of the linemen will move a little to take on a different person, or to create havoc in some way.  Or, they may be called upon to simply "fill a gap" which basically means that they take a position on the field, regardless of who is in front of him or what the offense is doing.
The linebackers in this scheme are right outside, right inside, left inside, and left outside.  The inside linebackers come up and try to stop a running play.  If the defensive linemen are doing their jobs, then the linebackers are free to make tackles (you hope!).  The outside guys are there to either take on an offensive lineman, play in run support, or to cover the running backs or tight ends who come out for a pass.  What this boils down to is that the outside guys have an assignment at the snap: watch the play and get a read.  If the offensive line moves backward, its a pass, and you have to cover a receiver; if they move forward, its a run, and you have to pick up a blocker, or fill a gap.  It gets complicated, and there is some instinct and some thinking happening.
In a conventional 4-3, the defensive line is a right end, right tackle, left tackle, left end.  The objective is the same, but now you have 4 guys against 5 offensive linemen, which changes the philosophy slightly.  Generally, this type of defense is better at stopping the run. 
Meanwhile, the linebackers become right outside, middle, and left outside.  Again, the roles are similar, but its now up to the middle linebacker to make the bulk of your tackles and to read the offense and attack the play.
By the way, the linebackers have other names as well.  They may be called "Sam" (with the S coming from Strong; the guy who lines up on the same side as the tight end), "Will" (with the W coming from Weak; the side away from the tight end), and "Mike" (M for middle). 
In the secondary, the corners should be covering the wide receivers in pass coverage, but should support and make tackles on running plays.   The strong safety is named because he's typically lined up on the same side as the tight end on offense.  That's the offense's strong side, so he's the strong side safety.  His job is first run support, and secondarily to cover the tight end in pass coverage.  The free safety is the guy who generally has no specific responsbility; he's free.  Typically, he'll support the deeper part of the field in pass coverage.
I think that gives the general idea of who's who on defense.  The coordinator can make this more "interesting" by electing to run "stunts" (having the defensive linemen switch places to confuse the offense, after the snap), or "blitzing" (from the German word for lightning, having someone unexpected rush the quarterback or to create havock on a run).
Or, just to make things more complicated, he can run a "Zone" defense where players are responsible for a zone on the field, rather than having players cover an individual.  It changes everyone's assignment, because now the players must adjust to having someone not otherwise involved in a way that's expected.
We'll discuss the zone among our advanced topics in a future lesson.
That's our lesson for today....class dismissed.
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