Comparing The 3-4 And 4-3 Defenses Part 1

The 3-4 defense appears to be the wave of the future. Over the course of the recent decade, the number of teams that have employed the 3-4 defenses went from 3 to 14. This season, almost half the league will be fielding a 3-4 to one degree or another.

As the pass has become more important, it makes sense that defenses are adapting by replacing larger, slower players with faster, more agile ones. The unpredictability of the 3-4 front makes the offensive line's job that much harder. The success of defenses such as the Steelers, Ravens, Jets, and even now the Saints, suggests there may be a substantial advantage to the 3-4.

Using the concepts of Expected Points Added (EPA) and Win Probability Added (WPA), we can compare the effectiveness of the two defensive schemes over the past 10 seasons. EPA measures every play in terms of the change in the potential gain of net point advantage. WPA measures every play in terms of how much it changed a team's chances of winning the game at hand.

Over the past 10 seasons, here is how the two schemes compare in terms of EPA, WPA, and yards allowed. (Negative numbers are good. Spikes, kneel downs, and aborted plays were excluded.)

Advantage of 3-4 In:Per Play Per Game
EPA Overall-0.018-1.20
EPA vs. Pass-0.010-0.35
EPA vs. Run-0.031-0.84
WPA Overall-0.00064-0.042
WPA vs. Pass-0.00046-0.017
WPA vs. Run-0.00093-0.025
Gain Overall-0.14-11.0
Gain vs. Pass-0.11-4.1
Gain vs. Run-0.25-6.9

Defenses employing the 3-4 have allowed 1.2 fewer EPA per game than 4-3 defenses. They have given their teams an additional 4% greater chance of winning each game, yielding 11 fewer yards per game than their 4-3 counterparts. The 3-4's advantage is sizable against both the run and the pass.

This does not mean that 3-4 defenses allow an average of 1 less point per game. Rather, they create one more point worth of net point advantage, in terms of points both scored and allowed, because defenses can create turnovers and other events that lead to scores. One point may not seem like much, but in terms of win probability, it's like taking an average .500 team and turning it into a .540 team. That's substantial.

It’s still not clear exactly how 3-4 defenses are able to achieve better success. 3-4 defenses featured a higher sack rate than 4-3 defenses, 6.6 % compared to 6.3%. But the 4-3 had a higher interception rate, 3.0% compared to 2.9%. I'll leave the question to the Xs and Os guys to debate.

Note: Because both offensive effectiveness and the number of 3-4 defenses have been increasing over the past decade, I had to account for year. To do this, I first compared 4-3 and 3-4 defenses within each season, then averaged those comparisons.

Ultimately, it may be that 3-4 defenses may simply have had better talent over the past decade, which would create the appearance that the 3-4 is somehow superior. In part 2, I'll account for individual team strength to get a better estimate of the true advantage of the 3-4 in the modern NFL.

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14 Responses to “Comparing The 3-4 And 4-3 Defenses Part 1”

  1. Anonymous says:

    Wasn't it determined that the interception rate is more dependent upon the offense than the defense, or at least has a stronger correlation? That could help explain why the rates are similar. Also, perhaps the 3-4 was too good at getting to the quarterback, getting sacks instead of a rushed throw being made for an interception.

  2. Anonymous says:

    You commented on talent at the end and that could very well have a lot to do with it. Many players are best suited to play a specific position. When there were only a handful teams playing the 3-4, there was less demand for 3-4 OLBs and NTs. Now that the split is roughly 50-50, a lot of teams are going to be looking at those guys in the draft and FA. Likewise, 4-3 DEs are suddenly in less demand on draft day and the top ones will be spread over fewer teams. It will be interesting to see how things progress now that about half of the league plays each way.

  3. Dave says:

    Is there any way to control for the overall talent level of the defense? I'm inclined to believe that the Steelers and Ravens would have two of the best defenses regardless of whether they played a 4-3 or a 3-4, and their choice of 3-4 might be skewing the data.

  4. johnnyjohnnywu says:

    "3-4 defenses featured a higher sack rate than 4-3 defenses, 6.6 % compared to 6.3%. But the 4-3 had a higher interception rate, 3.0% compared to 2.9%."

    I would be cautious in concluding that 6.6% is 'higher' than 6.3% and that 3.0% is 'higher' than 2.9% because the standard error is not taken into account and thus minor differences may not be significant.

  5. Chris says:

    The assertion made by anonymous that DE will be in less demand and thus find themselves concentrated into 4-3 teams is unlikely. 3-4 teams have realised that many 4-3 College DE can make a very good outside linebacker in their schemes. This explains why Sergio Kindle for example ended up in Baltimore. Brian Orakpo of the Redskins is another example.

  6. Chuck Winkler says:

    This makes sense, as that slight difference in reaction time between being on the line and slightly behind makes for better decisions in a 3-4.

    3-4 is also a much better zone defense. It would be interesting to see research done on which coverage is on average better.. man-on-man or zone. But again, player talent probably plays a big role.

  7. L.R. Gibson says:

    Perhaps I'm not reading the stats right but it seems that the chart shows that the 3-4 is actually better against the run than against the pass as the author suggests. If I am correct, then the run-pass balance should theoretically tilt even more to the pass league-wide correct? That is until teams began to utilize 5 and 6 man coverage with more secondary players.

  8. J.R. says:

    I'm with Dave. There are only 32 teams, and so if two or three teams that emphasize defense in their draft also happen to have excellent coaches and perennial Pro Bowlers (Ray Lewis, Troy Polamalu, Ed Reed, Suggs, Woodley, Harrison, etc. etc.) you're going to get skewed data.

  9. Brandon says:

    One additional factor no one has mentioned - familiarity.
    If only a handful of teams were using the 3-4 10 years ago, it may have been more effective because teams were mor eused to the 3-4. As time goes on, and the 3-4 is more common and the 4-3 less common I wonder if some of the current numbers may be closer together.
    I'm not saying the 4-3 is better or worse, just that it can take a while for opponents to adapt.

    And as someone pointed out - the personel required for each scheme vary and as one scheme becomes more popular , its harder to get the needed players, allowing the few teams that use the other scheme to more easily get those kinds of players.

  10. Anonymous says:

    This is a fairly murky analysis because the author really isn't even bothering to note the differences within both schemes. For example, the Cowboys and Chargers are a one gap 3-4. Yet, NE and Cle run the more traditional two-gap 3-4. But similar personell right? Uhh, not so fast. DeMarcus Ware and James Harrison are both great pass rushing OLBs, but totally different sizes and playing styles.

    What about 4-3 teams that rely on an underfront, where a DT is playing head-up on the center (just like in a 3-4) and features an OLB on the LOS over the TE (just like in a 3-4). Is there really a huge difference between that and a one gap 3-4? What if the team is partial to zone blitzing and like to drop that DE into the flat? Then the difference becomes even more negligible...

    Also, I specifically remember Dom Capers saying that when he served as Belichick's assistant in 2008, The Patriots only used their base defense about 10% of the time. How do we factor that in?

    I don't think this analsis is going to tell us anything.

  11. Anonymous says:

    The reason the 3-4 is better is you can use the hybrid form, i.e. Ravens defense and it looks like a 4-3 and it isn't or vice versa. And if linebackers were interchangable and were in constant motion no qb in the league could read it. So o-line failure would happen alot.

  12. Anonymous says:

    4-3 is good but man are 4-3 line man are expensive. So cost and advantages over rule the one weakness of 3-4, the 2 huge gaps between the DEs and NT. But for 3-4 to work great you need a top 7 linebacking corp. 3-4 isn't ment for all teams.

  13. Anonymous says:

    I think a lot of it has to do with how much emphasis 3-4 teams put in their front seven. It seems every 3-4 team spends their 1st and 2nd round picks there - the Pats for example had all their 3 down linemen as 1st round picks if I remember correctly. Of course you're going to have a better defense if you spend all your high picks there.

    I think the 3-4 just needs better players to make it work. You need those special, rare OLBs who can rush like a DE and cover like a LB. You need those rare monster NTs to hold all the double teams they get. And so on. A 4-3 team can get away with more average players there, and those teams usually seem to focus their top picks on offense or the secondary a bit more than the 3-4 teams.

    So maybe it's not so much a case of 3-4 or 4-3 being intrinsically better, but just that a 3-4 requires those rarer athletes and higher draft picks. Maybe the offenses of 4-3 teams are in general better than the offenses of 3-4 teams?

  14. Anonymous says:

    4-3 defense historically have created more dynasty teams such as The Steel Curtain Defense by the 1970's Steelers which they executed the 4-3 Defense, George Seifert's San Fransisco 49ers won 4 championships in a decade executing the 4-3 Defense and the 1990's Dallas Cowboys won 3 championships using the 4-3 Scheme. Even the 1970's Dallas Cowboys' {Doomsday Defense} was a 4-3 Defense under Tom Landry!

    All The Greatest Defensive teams of all time ran a 4-3 Defense such as The Steel Curtain, the Doomsday Defense, 46 Defense, the 2000 Baltimore Ravens, The Purple People Eaters.

    The 4-3 is more defensive end friendly and caters more to the Pass Rushers and it defends better against the interior run.

    The 3-4 defense is more friendly to the blitz scheme. It's more prone to more fluid linebackers who are more huge in size compared to those in the 4-3 Package.

    Guys like Martez Wilson or Jason Pierre Paul has such a quick release at the snap and able to rush the passer. in the Case of Martez Wilson, he hasn't have gotten much playing time under Steve Spagnola in the 4-3 scheme.

    J.J. Watt is more suited for the 3-4 because of his size and the scheme that spreads out the texans' linebackers which gives him more room to rush the passer with ease. If he was in the 4-3 scheme he would have to articulate more athleticism like Junior Galette for the Saints when he does the Dwight Freeney Spin Move to elude the Offensive Tackles barricade.

    John Abraham can work in both 3-4 and 4-3 because he has the quick release and he's athletic.

    Richard Dent under the hybrid 4-3 Defense called the 46 Defense recorded 17 sacks for 2 consecutive seasons as a chicago bear which is a rare accomplishment as far as i know and the team that he played for in 1984 set a all time record with 72 sacks!

    The 1992 Cowboys was number 1 overall in Defense using the 4-3 scheme while the New Orleans Saints was number 2 overall in defense using the 3-4 scheme which is funny because he usually look like they in a 4-3 scheme under Steve Sidwill.

    The Pittsburgh Steelers had 5 shutout games in the 1976 season using the 4-3 scheme and the 2000 Baltimore Ravens under Marvin Lewis as the Defensive Coordinator had 4 shutout games!

    And Notice how there were more shut outs by 4-3 Defense than shut outs from the 3-4 Defense for the 2012 Season!

    The New Orleans Saints shutout the Tampa Bay Bucs 41-0, they were 4-3 team.

    The Oakland Raiders shutout the Kansas City Chiefs 15-0, they were a 4-3 team.

    The Atlanta Falcons shutted out the Former Defending Super Bowl Champs, New York Giants, 34-0

    The Seattle Seahawks shuts out the Arizona Cardinals 58-0, they were a 4-3 team.

    I can only think of one team that plays a 3-4 Defense that shutted out a team and that was the San Fran 49ers when they defeated the Jets 34-0

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