However, in 2011, the one-time lowly Houston Texans made their case for the 3-4 defense with a remarkable turnaround.
After Houston's defense was ranked 30th in the NFL in 2010, the Texans brought in new defensive coordinator Wade Phillips, who had just been fired from the Dallas Cowboy head coaching position. Wade had the Texans switch from a 4-3 to a 3-4 defense.
The Texan defense subsequently went from 30th in the NFL to second. In the regular season, the Texan defense was second in yards allowed per game (285.7), fourth in rushing yards allowed per game (96), and third in passing yards allowed per game (189.7).
Last season, new Cougar offensive coordinator Brandon Doman received a large dose of his coaching experience facing the 3-4 Cougar defense before the season started. While facing various defensive schemes over the course of last year, Coach Doman felt one defensive scheme was particularly difficult to prepare for.
"Oh yeah, our defense is probably the toughest defense to face," said Coach Doman. "At least, that's been my experience as an offensive coordinator facing these guys so far."
More than likely, that's because of the flexible nature of the 3-4 defense. Players in a 4-3 defense are more specialized in what they do, thus forcing the hand of the defensive coordinator.
For example, by placing the two best pass-rushers in the 3-4 on the outside, the linebackers can either act as a stand-up defensive end or drop back into coverage based on the defensive call. Conversely, defensive tackles within a 4-3 are more specialized, creating less confusion for opposing quarterbacks and running backs.
"Yeah, [the 4-3 defense is] a little more base and a little more standard," said running back coach Joe DuPaix. "You know where things are coming from, where [in] a 3-4, man, they can bring it from anywhere."
However while there might be more flexibility and less predictability up front in the 3-4 system, there is a compromise.
"You're not going to have as much meat up front [on defense], and so if we can get a good push and create a couple seams, you've got some big-play potential," DuPaix said about facing the 3-4 defense. "Again, there's some pros and cons to both and I don't have a preference."
Another advantage of the 3-4 is that it provides more speed and agility.
"They can bring a backer and back him up, or they can bring a safety on the pressure," Coach DuPaix said. "They can do some different things as far as bringing the inside backers or the outside backers, so there's more moving parts with the 3-4."
In a 4-3 front, a defensive tackle is almost always in a one technique (on one of the outside shoulders of the center) while the other is almost always in the three technique (on the outside shoulder of the guard). The linemen in a 4-3 are typically responsible for one gap on a run play and producing more pressure on passing plays.
The interior lineman in a 3-4 are responsible for either one or two gaps and the pass rush can, and generally does, incorporates linebackers out of the base defense if desired. That is why it's important that the interior linemen demand a double team, and this can be achieved by positioning the tackles in a three technique (between the guard and tackle).
When it comes to running against either the 4-3 or 3-4 defense, Coach DuPaix acknowledged the different challenges both schemes provide.
"It's different, you know, if you're a 3-4 then your running text will be a little different than if it's a 4-3," said Coach DuPaix. "It's not so much about what they do or what they prefer but about what we do and how we execute it. The 4-3 seems like it might have more of a stability to it, but the 3-4 is going to maybe have more moving parts."
While Coach Doman might feel that the 3-4 defense poses more of an overall challenge, Coach DuPaix doesn't have a preference when it comes to which type of defense he would rather attack in the trenches.
"My opinion on that is that they're both really good and we have schemes against both of them," said Coach DuPaix. "There are different things you can do out of a 3-4 and 4-3 that present different challenges, but there's also things we can do to counter those things. As far as a preference? I don't really have one."
It is interesting to note that 12 of the 32 NFL teams now run a 3-4 defense, and three of the first 11 picks in last year's NFL draft were initially taken for 3-4 defenses.
In the playoffs last season, the Steelers, Packers, Texans, Patriots, Ravens and 49ers all used the 3-4 defense, while the Giants defeated the Patriots 21-17 in the Super Bowl with a 4-3 defense. Let the debate continue.