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he 3-4 Defense

The Basic 3-4 Defensive Alignment

Another popular defensive alignment is the 3-4. This defense was used by Bill Parcels

and his N.Y.Giants to win a couple of superbowls. From 2000 to 2004 it was also used byBill Parcels' former defensive coordinator and now head coach of the New England

Patriots, Bill Belichick, to win three more superbowls. This defense is now becomingquite popular again. The NFL is very much a copy-cat league.

In the 4-3 defense, you need two very large and athletic defensive tackles and two

somewhat large and very athletic defensive ends. These guys are very hard to find. It

seems there's about one excellent defensive end prospect in each draft, which is not

nearly enough to go around. If you can't find a couple of good defensive ends, you're infor a long season of living and dying by the blitz.

One reaction to this has been to develop the 3-4 defense. In this defense, you need one

really large nose tackle. This NT has to be a real monster of a guy, 350 pounds or so,

because his job is to take on the center and one of the guards simultaneously on everysingle play. Then you get two more defensive tackles at around 300 pounds each, and

play them up against the offensive tackles. All three of the defensive tackles have what is

called two-gap responsibility. They are expected to hit the offensive linemen head on,and watch the play to make sure the running back doesn't come through on either side of 

them. Also, they're expected to hold their block so that the offensive linemen can't get out

and block a linebacker.

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In the 3-4 system, the linebackers are expected to make most of the plays. In the 3-4

system, the DTs play a more physical game as they are taking on one or two offensive

linemen directly, play after play. Unlike the DTs in the 4-3, the DTs in the 3-4 areresponsible for every single gap in the offensive line. Although the DTs get relatively few

chances to make tackles or sack the quarterback, anything bad that happens is still

ultimately their fault.

In the 3-4, you have four linebackers. Two of these guys are inside linebackers, and areexpected to weigh roughly 240 pounds and be quite athletic. You also have two outside

linebackers. These guys are sometimes called "tweeners," as they are in between the

normal size of defensive ends and linebackers. These guys should weigh perhaps 255-265pounds and also be quite athletic. Because these are linebackers, they tend to be faster 

than the heavier defensive ends. Their presence makes it much more difficult for the

quarterback to roll out, as he will be rolling out directly into the path of one of theselinebackers.

In the NFL there are many running backs who are incredibly athletic. O.J.Simpson wasperhaps the first of these, but today there are perhaps a dozen of them. These guys are

very shifty and hard to chase down. Defensive linemen simply can't do it. So the solutionwas to remove one of the DL from the defense and substitute a fourth linebacker. These

linebackers have the speed to chase down such running backs. The 3-4 defense was

motivated by two factors: the difficulty in getting good defensive ends, and the need tostop very fast running backs. This is the strength of the 3-4. The DTs keep the offensive

linemen off your linebackers, leaving them free to roam the field and bring down runners.

Unfortunately, the 3-4 has a weakness. Three DTs cannot reliably collapse the five

offensive lineman pocket on the quarterback, so it becomes much harder to pressure the

quarterback. Traditionally, the 3-4 has struggled against the pass. The modern solution tothis problem was worked out by Dick LeBeau, and it's called the Zone Blitz. In a normal

blitz package, you have five or six guys rushing the passer. The remaining linebackers

and defensive backs often played man coverage, which is relatively dangerous. Widereceivers in the NFL tend to be taller than defensive backs, so they often win the one-on-

one battles.

In the 3-4, you select your four linebackers for the speed to drop back and cover a zone.Since there are four linebackers, the quarterback cannot guess which one of the four will

rush on any given play. Whichever linebacker rushes, it's relatively easy for the other 

three to shift around a bit and fill in the zones. Sometimes the defense will rush two

linebackers on the same side, so there are two defensive tackles and two linebackersattacking three offensive linemen. The remaining two linebackers again can quickly shift

over to fill in the gaps left by the two who are blitzing.

If the 3-4 defense finds itself late in a game protecting a lead, there is no need to switch to

a prevent defense. Since all four linebackers are skilled in coverage, you can just drop allfour of them into zones, playing eight men in zone coverage. It's next to impossible to do

this with a 4-3 defense.

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The 3-4 defense can have trouble matching up against a very fast offense. It's important

for the success of the 3-4 in these cases for the defense to play an extremely physical

game, jamming the receivers hard at the line of scrimmage. In the 2002 superbowl, thePatriots looked like their defense matched up poorly with the numerous fast receivers of 

the Rams, but by playing an intensely physical game the Patriots managed to slow the

Rams enough to eke out a win. Similarly, in the 2004 playoffs the Patriots hosted theColts, and again it looked like a bad match up for the Patriots. But by making the Colts

play a more physical game than they were used to, the Patriots managed to almost

completely shut down the Colts offense. Had this game been played indoors inIndianapolis on carpet instead of outdoors on grass in cold weather, it's quite plausible the

Colts would have found a way to exploit the lack of speed in the Patriots secondary.

So in summary, the more traditional 4-3 offense seems better suited to the modern pass-

friendly NFL rules, while the 3-4 offense seems more geared to stop the run basedoffenses of the 70s and 80s. However, by mixing up the rushers and zone coverages to

confuse the quarterback and by forcing the receivers to play a far more physical game

than they would wish, the 3-4 has been successful at the highest levels, in spite of it'sapparent drawbacks.