The Statistical Reason Why The Packers Defense Has Declined
While doing research on my last article, I noticed one very interesting fact: Dominant 3-4 defenses tended to have a star 5-technique defense end. The 3 best 3-4 defenses in terms of dEPA (defensive expected points added) in the NFL right now are San Francisco, Arizona and Houston and each team boasts impact 5-technique defensive linemen like Justin Smith, Calais Campbell and JJ Watt, each of which is among the top five 5-technique defensive linemen according to ProFootballFocus. This got me to thinking: everyone knows that the quarterback effects offensive success more than any other position on the field (hence why Aaron Rodgers and Peyton Manning can keep winning games without good offensive lines and running backs), but is there a position on a 3-4 defense that is most important to defensive success?
Traditionally, the hallmarks of a good 3-4 defense has been it’s nose tackle and outside linebackers; indeed in 2009 when Green Bay switched from a 4-3 to a 3-4 defense, general manager Ted Thompson drafted nose tackle BJ Raji with the 9th overall pick and then traded up back into the 1st round for outside linebacker Clay Matthews III. The argument has always been made that a dominant nose tackle that can eat up multiple blockers and outside linebackers who are athletic enough to rush the passer are the keys to a dominant 3-4 defense. You could argue that Green Bay seems have both positions covered, both Clay Matthews III and BJ Raji are both dominant players but while that seemed to have translated to success in 2009 and 2010, it didn’t seem to matter much in 2011 and 2012.
What I’ve done is a correlation analysis using ProFootballFocus’ player grades and comparing them to overall defensive efficiency measured in dEPA. I’ve flipped the signs for dEPA to just to avoid making it an inverse correlation. I’ve included both Pearson’s r and chi2, I’m not really much of a statistics guy so I have no idea what the difference is between them, but if you happen to know more about this, leave a comment and I can adjust my analysis if needed. Overall, the way to read these figures is that a value of 0 means there is no correlation at all while a value of 1 means that there is perfect correlation. So for this case, the higher the number the more “valuable” that position is to defensive efficiency. I’ve also included a positive control by correlating dEPA vs. dDVOA (from Football outsiders) and they are 91% correlated, which basically means this analysis holds for both metrics. Finally, I’ve included a negative control by looking at the correlation between how well the offensive center plays versus how well the defense does; presumably how well the center plays has no relationship to how well the defense plays.
|Parameter||Pearson r||X 2|
The results are pretty striking. First off nose tackle seems to be completely irrelevant in the 3-4 defense to the point that it appears that it’s more important how well your center plays than your nose tackle when it comes to defensive efficiency. A great example of this is that the best 3-4 nose tackle combination in the NFL in 2012 was Jay Ratliff and Josh Prince-Brent but the Cowboys were the 3rd least effective 3-4 defense in 2012. On the other hand San Francisco had the best 3-4 defense this year but featured Issac Sopoaga, who graded out as the worst 3-4 nose tackle.
Moving on to outside linebackers, it appears even worse where the better a team’s outside linebackers, the worst the defense is overall. While I wouldn’t say that the Packers should go out and find some bad outside linebackers (as they have the worst 3-4 outsider linebacker in the NFL in Erik Walden), there isn’t any statistical correlation between how well outside linebackers play and how well the defense plays. Some of the best 3-4 outside linebackers played on terrible defenses this year; Justin Houston (KC), Victor Butler (DAL), Ryan Kerrigan (WAS), DaMarcus Ware (DAL) Lamarr Woodley (PIT) and James Harrison (PIT) all have overall positive grades according to ProFootballFocus but played on some of the worst 3-4 defenses this year. On the other hand, Houston seems to have shown that you can have a dominant 3-4 defense with Brooks Reed (-.9), Connor Barwin (-19.0) and Whitney Mercilus (-13.8).
So what seems to be the most important position in a 3-4 defense? Apparently it’s 5-technique defense end and safety. In other words, the better your defensive ends and safeties are, the more effective your 3-4 defense. If this doesn’t strike you as cathartic nothing will. In 2009-2010 the Green Bay Packers had a dominant defense, which included defense end Cullen Jenkins, and safety Nick Collins. In 2011-2012 they did not. More importantly, Green Bay hasn’t managed to recover from losing both of them.
Below I’ve run another correlation analysis looking at how well the defense ends and safeties have played compared to overall defensive efficiency over the period of 2009-2012 (the years where the Packers played a 3-4 defense). The results are rather startling; defensive end play had a Pearson’s r of .7455 while safety play had a staggering Pearson’s r of .9115 (again a value of 1 is perfect correlation). I think both results shouldn’t be all too startling when you think about them. A perfect example of how important defense end play is when you consider the effect that DE Justin Smith had on the San Francisco defense; with him, OLB Aldon Smith was on pace to break the NFL sack record, but without him Smith hasn’t managed a single sack. In terms of efficiency, Aldon Smith managed a grade of 1.37 per game with Justin Smith in while grading out at -.76 average for every game Justin Smith was out.
|Parameter||Pearson r||X 2|
I don’t think any fans were thinking that losing Jenkins and Collins would be a improvement, but I doubt many really knew the true affect that both players had on the defense. It could be argued that if Collins hadn’t been lost with a neck injury in 2011, the Packers very well could have won back to back Super Bowls.
Luckily, it’s not all bad news for the Packers; wisely it might seem as if the Packers already know this (heaven forbid if I’m the first person to notice this trend), which might explain why BJ Raji has been spending less and less time at nose tackle and more and more time at defensive end (where he actually has a +12.1 grade). While safety Morgan Burnett isn’t as good as Nick Collins, he is still a good player and maybe with a season or two more of experience will be able to fill Collin’s shoes; perhaps adding Charles Woodson at safety full-time might make the situation better. Furthermore, adding Mike Neal and Jerel Worthy are active attempts to improve the defensive end position. However, I wouldn’t be all too surprised to see a safety or another defensive end drafted fairly high in this years NFL draft.
Thomas Hobbes is a staff writer for Jersey Al’s AllGreenBayPackers.com.