Does the Arizona Cardinals defense really need an elite pass rusher?

It feels like the Cardinals have been chasing an elite edge rusher for their 3-4 defense for decades. From free agents to draft picks, the team has failed spectacularly at acquiring and grooming pass rushing talent. Yes, I'd rather see Sam Acho scrambling around out there than Chike Okeafor or Joey Porter, but I think they'd be just as well off calling up Bertrand Berry as relying on Lorenzo Alexander or O'Brien Schofield for a whole season. Can recent draft pick Alex Okafor surpass the achievements of Cody Brown or Will Davis? Considering Brown never even saw the field and Davis only lasted two seasons in the NFL, the bar is about as low as it could be.

Even though every outside linebacker who has donned a Cardinals jersey has failed to meet expectations since the team began converting to a 3-4 defense in 2008, the Cardinals finally put together one of the league's top overall defensive units in 2011 and 2012. That they were able to make such an improvement without a significant influx of talent speaks to the importance of a competent defensive coordinator, but is there any correlation between an elite defense and an elite pass-rusher? Given the league's emphasis on top-flight quarterbacks, it seems logical to assume that one of the best ways to counter an offense would be by disrupting the QB, and one of the best ways to do that in a 3-4 defense is to bring an outside linebacker off the edge.

Looking over some team statistics from 2012, one could make a case for the 49ers, Texans, Steelers, Jets and Cardinals as top 15 defenses that ran a 3-4. The following chart breaks down the percentage of sacks each team got from their outside linebackers.

- via ESPN.com

As you can see, San Fran got a lot of production out of its outside linebackers, particularly Aldon Smith, who picked up 19.5 sacks on his own. The 49ers were also the best defensive unit in this group, possibly in the entire NFL. Houston's biggest contributor was a defensive end, J.J. Watt. Their outside linebackers were some of the least productive in the league but the team still got pressure, netting the fifth-most total sacks in the NFL. This is an incomplete picture, though, one that would benefit from breaking down QB hits and pressures per team but, alas, I can't find those stats.

To give some context to the previous statistics and derive at least a little meaning from them in regard to the overall picture -- ie, how having an elite edge rusher affects the 3-4 defense -- let's take a quick look at sack percentage. This is the percentage of passing plays against your defense which resulted in a sack. It's more meaningful than just looking at the total number of sacks a defense accrued in the season; if offenses weren't passing as much against one particular team's defense, that team wouldn't have the opportunity to pick up as many sacks (as in the case of the Cardinals), skewing the numbers.

- via sportingcharts.com and NFL.com

There is a discrepancy in this chart. The Jets' low sack percentage doesn't really seem to inform their seventh-best opponent passer rating. Presumably, the Jets held up well enough in coverage to mask their pass-rushing deficiencies. Maybe I need to start giving Antonio Cromartie more credit.

The Jets' stats point to the two-way street of pressure and coverage. In the simplest of terms, the quicker you can get to the quarterback, the less time he has to throw, making it easier on your pass defenders. The fewer players you need to get to the QB, the more players you can drop into coverage, potentially buying more time for your rushers to get home. This is what makes blitzing a double-edged sword. If your extra rushers don't get to the quarterback quickly enough, he'll have an easier job of deciding where to throw the ball and of getting it out in time.

When you put it all together, you can conclude this: good defenses disrupt the quarterback. It doesn't appear to make a huge difference if it's the outside linebackers doing it, the defensive ends, or an even distribution among the front seven. An elite edge rusher can make a good defense a great one, like Aldon Smith in San Francisco, but he can't single-handedly make up for a sub-par group around him (Clay Mathews and Green Bay's otherwise-sorry lot being one example).

Having an elite rusher opens up new possibilities for a defensive coordinator. One player who can be consistently relied upon to create pressure from the edge makes the play-caller's life that much easier. Instead of relying on blitzes, which deplete the number of run and pass defenders by asking them to rush the quarterback, the team can approach each week with a more flexible gameplan, dictating the flow of the game with whatever mix of pressure and coverage they think best suits each particular match-up. In some ways, an elite pass-rusher is comparable to an elite quarterback. Both make their coaches look a heck of a lot better.

The Cardinals, Steelers and Jets showed last year that you don't need to have "that guy" coming off the edge every snap to put a good defense on the field. It's a good thing, too, because it's pretty obvious that the Cardinals still haven't found him yet. Without that menace, the secondary is put under extra stress, being tasked with maintaining good coverage for a longer period of time. Additionally, it becomes the job of the coaching staff to build pressure into the scheme. By switching to a one-gap system, the Cardinals hope to compensate for the lack of an edge-rushing menace with the defensive line. Calais Campbell and Darnell Dockett are a good pairing for the job, but it's up to Todd Bowles to make sure every man is put into a position where he can succeed.