A lot of this has probably been said but here's what I think.
In a 4-3 you obviously have 4 linemen instead of 3 in the 3-4. You don't need as big personel here whereas with 3 linemen you're gonna need some huge guys up front to give protection to the linebackers. Some teams just don't have that. A 4-3 allows you to put some faster smaller guys say at end. 4-3 gives good flexibility between run and pass stopping and is more suited to run stopping than the 3-4 cause you got 4 linemen instead of 3 (and more gaps covered by linemen).
With the 3-4 you only got 3 linemen. In a typical pass rush you got 4 guys rushing so in the 3-4 one of those guys will then be a linebacker. This can serve to confuse the defense about the direction the pass rush comes from. With a 3-4 you need really good linebackers cause there are less linemen to cover O-Linemen on rushes. Also you need a really good big nose tackle who can effectively clog up the middle and take on 2+ guys at once.
So the main advantage of the 3-4 and the main reason it's used is due to the chaos it creates for opponents offense with linebackers rushing from all the place. But, heavy pressure can be tough on the secondary so the 3-4 if too agressive can also be weak against the pass.
It takes a specialized group of personnel to run the 3-4...
With 3 down linemen it's more difficult to stop the run... In general, you need a very talented nose tackle to clog up the middle, as well as very mobile DE's that can beat double teams to seal off the edges...
Most of the pressure you generate comes from the linebackers, so you need guys with a lot of speed that can generate a pass rush from further off the line, but are still large enough to shed blocks from 300 pound O-linemen...
This is why, in the draft, you typically hear guys referred to as a "good 3-4 linebacker" or a "good 3-4 end." These guys are normally 'tweeners... Guys that play DE in college, but are a little undersized are often referred to as "3-4 linebacker prospects." A good example of this is Demarcus Ware... And guys that played DE in college, but are maybe a little oversized and better at stopping the run than generating a pass rush are often referred to as "3-4 prospects." You will also sometimes hear of undersized DT's referred to as "3-4 DE prospects."
The 4-3 is the more common collegiate system, so guys tend to be able to stay at their natural positions when they make the switch to the pros... The 3-4 tends to require that rookies change positions from their collegiate position and/or change duties within the position... This makes the learning curve much steeper, and is probably why the bulk of NFL defenses shy away from implementing it...
Another reason why it is not as common as the 4-3 is the relative scarcity of nose tackles that can compete in the pros... You need a guy who is both massive and extremely mobile at the nose to run the 3-4... This guy is going to face double teams play after play after play, so he also has to have a great deal of endurance... A good example is Haloti Ngata with the Ravens... It's rare to find these guys... Normally when you find a guy large enough to play nose in a 3-4 he doesn't have either the mobility or the endurance to pull it off... It's rare to find the combination of size, mobility, and endurance necessary to pull it off, and often times the guys that possess these traits were made offensive linemen very early in their football careers...
The players make the defense as much as the plays that are called, so if you have a glut of good LBs then you want 3-4. If your defense is more balanced, run a 4-3. And if your defense is terrible, also run a 4-3. It seems that most players, good or bad, have spent tons of time in the 4-3 and it's the best option for a crappy defense.
For instance, not so long ago the Washington defense had Lavar, Trotter, Armstead, and Washington (I may be getting this wrong...players switch in and out so often it's hard to tell. It could've been Pierce). I advocated the 3-4 for this team because the D-line stunk and one great LB was always on the sidelines, whether it was Armstead or LaVar.
The 4-3 defense is different than the 3-4 in that the 4-3 has four defensive lineman and three linebackers while the 3-4 has three defensive lineman and four linebackers.
Both differ from the 46 defense, popularized by Buddy Ryan when he was with the Bears.
In this defense, you'd have four lineman and six linebackers. It puts the team at a disadvantage because you're only playing 10 players when you could play 11. Buddy Ryan was so confident in his D that he felt he didn't need the 11th man.
This isn't to be confused with the 46 defense that Barry Switzer tried in one game with the Cowboys. Switzer didn't fully grasp the concept and put 46 players on defense. The team was promptly whistled for 46 men in the huddle and Switzer abandoned his variation of the 46 defense.
Something else about the 46 defense, you need very good cover corners for that or a good QB can take advantage of a burnt corner and single safety real quick. Better offensive schemes is what led to the demise of the 46 as a viable full time defense.
Something else about 3-4 and 4-3 defenses that some people made some confusing comments on though, it shouldn't be the depth that determines what alignment to go with. Just because a team has a lot of LBs does not mean it can successfully run the 3-4. Like everyone has said, specialized personnel are needed to run the 3-4 successfully. Those "tweeners" Plindsey mentioned are crucial.
There are also variations in the 4-3 scheme that are pretty different from team to team too. Someone mentioned the defensive linemen who shoot the gaps, trying to make plays in the backfield. Tampa 2 defenses seem to depend on this style more than others, going with smaller and faster linemen. Then there's the championship Baltimore defense that used two fat DTs in the middle who clogged up o-linemen so LBs could roam freely to make plays.
Actually in the rest of the English speaking world it is spelled "defence" - for some reason Americans changed it to "defense".
While I agree, whenever this issue comes up I point out that this is American football. So it seems logical one would use the American spelling. Otherwise, we may become confused thinking they're talking about the 4-3 vs. the 3-4 defence in futbol, which in such cases would not include the bloody keeper.
beanoX3 wrote:Something else about the 46 defense, you need very good cover corners for that or a good QB can take advantage of a burnt corner and single safety real quick. Better offensive schemes is what led to the demise of the 46 as a viable full time defense.
I've always hoped some team would man up, put a load of money into getting Champ Bailey and Ronde Barber or Chris McAlister, and then play a 46 and flat out dominate defensively. That sure would be fun to watch at the very least, though I'm not so sure it would actually work as it theoreticall should.
I'd also like to see a team like NE or Car in the midst of an RBBC use the wishbone formation, though realistically that will never happen because for whatever reason NFL coaches don't like any formation or play set that is associated with any form of the option. Aside from the Falcons that is.
beanoX3 wrote:Something else about the 46 defense, you need very good cover corners for that or a good QB can take advantage of a burnt corner and single safety real quick. Better offensive schemes is what led to the demise of the 46 as a viable full time defense.
I've always hoped some team would man up, put a load of money into getting Champ Bailey and Ronde Barber or Chris McAlister, and then play a 46 and flat out dominate defensively. That sure would be fun to watch at the very least, though I'm not so sure it would actually work as it theoreticall should.
I'd also like to see a team like NE or Car in the midst of an RBBC use the wishbone formation, though realistically that will never happen because for whatever reason NFL coaches don't like any formation or play set that is associated with any form of the option. Aside from the Falcons that is.
I don't think it would work, simply because corners can't be as "physical" (if you can even call it that) anymore. Even Deion would ride guys hips and cut off their routes. Guys get called for that now. You just can't ask even the best corners to shut down good receivers for a whole game anymore. The game downfield is called too tight.
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by bobbing_headz » Fri Dec 01, 2006 12:29 am 
