The 3-4 features three down linemen, four linebackers and a four-deep secondary. The 4-3 has four down linemen, three linebackers and a four-deep secondary. There was a time not too long ago that 90 percent of the NFL lined up in a 4-3 defense, but coaches steadily have begun to see the merits of a 3-4 when it comes to defending the modern offenses. With the three new additions, 13 of the 32 teams now line up in some form of the 3-4. The AFC actually has more 3-4 teams than 4-3 teams (nine to seven). Just as the West Coast offenses came into vogue after being influenced by the Bill Walsh era, many of the 3-4 teams are offshoots of Bill Parcells or the Pittsburgh Steelers.
Why are clubs turning to the 3-4 package? Kevin Colbert, the personnel man in charge of building the Steelers, once said to me it was great back when Pittsburgh was one of the only teams in a 3-4 because the Steelers were looking for different types of players and there weren't many teams looking for the same players. Now, the Steelers have to work a lot harder to find personnel. Keep in mind, the majority of college programs use a 4-3, which means NFL clubs have to do some speculating as to whether a player will fit into the 3-4 scheme at the next level.
A 4-3 defensive lineman is typically a guy that wants to get out of his stance as quickly as possible and beat an offensive lineman into the backfield. That is called a "one-gap player." A 3-4 defensive lineman wants to strike the offensive lineman and control the line of scrimmage, which is referred to as a "two-gap player." One-gap linemen can be smaller and explosive. Warren Sapp was the prototypical 4-3 tackle. A 3-4 lineman is usually much taller with long arms and more bulk. Richard Seymour of the Patriots is what every 3-4 team is looking for nowadays. Most personnel people would tell you that it is easier to find two-gap linemen that can play in the NFL than it is to find great one-gap penetrators, which is one thing that is appealing about a 3-4.
No matter what defense a team runs, getting to the quarterback is a primary function. There is a notion that it is easier to find the James Harrison- and LaMarr Woodley-type pass rushers for a 3-4 than it is to draft a Julius Peppers or Mario Williams to play defensive end in a 4-3. An undersized college defensive end usually does not appeal to a scout looking for a 4-3 end, but a 3-4 scout will look at that same undersized player and project him to be an outside linebacker and, after teaching him some basic zone pass-drops, an inexpensive pass rusher who could be drafted after the first round.
Some people believe the most effective pass rush in the modern game comes from the 3-4, but the numbers suggest something a bit different.
Take a look at the following categories from the 2008 season. Here's a look at the top five teams in both packages. There were 12 players that produced double-digit sacks last year. Four from 3-4 defenses, and eight from 4-3 defenses. Granted, only 10 teams rushed the passer from a 3-4 defense in 2008 -- or 31 percent of the teams -- but four of the 12 players to produce double-digit sacks is 33 percent, which doesn't suggest that the 3-4 is going to provide much more of an advantage on an individual basis.
While there's a slight advantage for the top 3-4 defenses in overall sacks and a small edge in rush defense for the top 4-3 squads, neither is enough to say that one package is superior to the other.
An intriguing aspect of the 3-4 defenses is flexibility. With one less person in a three-point stance, it is easier to make adjustments to all the exotic formations offenses throw at a defense. Many coaches don't want to be in a four-man rush if the quarterback is in the shotgun formation and has emptied the backfield, thus building a formation with three eligible receivers to one side and two receivers to the other side. A 4-3 team has to pop a lineman out of his stance and stand him up as a pass dropper. A 3-4 team is already set to make the adjustment.
One coach switching to a 3-4 defense told me he likes the idea of more players standing up so they can pursue the ball. After examining forced fumbles and runs over 20 yards -- two areas that should indicate if having that extra player in pursuit makes a difference -- the top five 3-4 teams gave up a total of 29 runs over 20 yards last year, while the top five 4-3 teams gave up a total of 37 runs of more than 20 yards. Score a point for the 3-4 teams.
When it came to forced fumbles, which can be caused by getting more people to the ball carrier (most coaches instruct the second and third tacklers to go for the ball), the top five 3-4 teams forced 96 fumbles while the top five 4-3 teams forced 111 fumbles. Hard to make a case that the design of the front made a big difference in pursuit.
After sitting down with a club contract negotiator, he thought there might be a slight difference in financing a 3-4 than a 4-3, which is very interesting. Guys such as Julius Peppers and Mario Williams cost more to put on the field than James Harrison or Joey Porter. A defensive tackle such as Kevin Williams or Albert Haynesworth could be a lot more expensive than a Brett Keisel or Jason Ferguson. The truth is a premier player in the 3-4 such as DeMarcus Ware, is expensive. However, there may be some truth to the overall cost of a solid 3-4 like Miami's is cheaper than a 4-3 like Minnesota's front.
Finally, players -- not schemes -- make a defense go. Last year, we witnessed the Steelers in their 3-4 defense win a Super Bowl. The year before that, it was the New York Giants' 4-3 package that was relentless in getting after Tom Brady on their way to a Super Bowl win. The flexibility of the 3-4 is great, if you have a nose tackle that can force a double-team block. The 4-3 front is productive if a team can have two tackles like the Williams wall in Minnesota and Jared Allen coming off the edge.