I made this article in response to ScarletO's excellent post on the need for cornerbacks in a good defense. To preface, I agree with Scarlet in premise, but I disagree with his conclusions that Pass rushers play less of a role in a defense than we generally think. I'm generally taken aback by this comment:
With the Giants winning the Super Bowl a few months ago, it is easy to assume that a powerful pass rush is the key to victory in the NFL. Improving the pass defense to make it difficult on opposing quarterbacks, however, seems to be closely linked to the quality of the secondary.
Once again, I think that Scarlet makes a great point, but he is giving pass rushers a short shrift, and inflating the importance of the Secondary slightly.
I'm always wary of anointing one group as more effective towards a better defense than another.
Case in point: It is very true that sacks have little correlation with passer rating. However, that makes sense. Why? Because when QBs get sacked they don’t throw the football, i.e. they cannot possibly affect their QB rating that play.
I have never prescribed to the theory that QBs who are sacked more are going to be quicker and more anxious with their passes than QBs who are not. If a team allows 50 (A bad O-Line plus a QB who takes a while to make decisions) sacks a year that means they are allowing 3.1 sacks/game. If there are 50 total offensive plays, and the team has a 60/40 pass/rush ratio that means that only 10.3% of offensive passing plays is the QB affected at all by sacks. That’s not counting the plays he takes off for rushing plays (6.2% sack rate). To put that in perspective only 4 teams allowed 50 or more sacks in the league last year. 28 teams had even fewer sack percentages than this If you think that’s going to affect the top 32, ostensibly, QBs in the world than I can't help you.
So far, I have only offered reasons for why pass rushers are misunderstood. However, I believe there are two sets of stats which can more adequately describe their roles:
First, let’s take sacks out of the equation. Our real focus should be how much QB Hits and Pressures affect passer rating.I would be willing to bet that these two stats affect passer rating. 3 years ago Pro Football Focus did an article on just this. In their article "Beware the Use of Sack Statistics" they lay out the situation well:
The point is that sacks are only a minor subset of pressure. Last season, across the league, they accounted for only 16 percent of all pressure when hits ad pressure on the QB are included. A hit is when a QB is knocked down but not sacked and a pressure is when a QB is forced to move in the pocket in some other way than simply stepping up into a throw.
Hits and pressures are going to force a QB to get off his throws more quickly so that he can complete the play and not be sacked. It is not a given that someone with the most sacks will get the most pressures and QB hits as well:
Taking things from a different perspective, sacks have been the measure of pass rushers for years but again, it’s only part of the whole story. Defensive end Ray Edwards of Minnesota managed just 6 sacks in 15 games but also weighed in with 14 hits and 33 pressures. The other piece of missing information is how many times he actually rushed the QB — 492 times, in this case. That’s a lot more pressure than the average DE from that many rushes.
On the other hand, Joey Porter of Miami rushed the passer 567 times and sacked the QB 17 times but managed only an additional 9 hits and 24 hurries. Porter gets notoriety from the sacks but an average 3-4 OLB, going after the quarterback as often as he does, should actually get more pressure.
Further, hits and pressures have been shown to negatively affect Passer Rating.
Second, If we want to see how sacks affect a game we should use NY/A which calculates (Total Yards gained-Sack Yards)/All Passing Plays:
GB NY/A 8.3 Sacks allowed 41
NE NY/A 7.9 Sacks allowed 32
NO NY/A 7.8 SA 24
NYG: NY/A 7.7. SA 28
SD NY/A 7.2 SA 30
Oak NY/A 7.2 SA 25
Phi NY/A 7.0 SA 32
Pitt NY/A 7.0 SA 42
Hou NY/A 7.0 SA 33
Det NY/A 6.9 SA 36
League Average: NY/A 6.3 Sacks allowed 37.1
Over a random sampling of four years there is a statistically significant negative correlation between Sacks allowed and NY/A. 8 of the top 10 teams in NY/A had below league average Sacks Allowed. Teams with a higher NY/A tend to win more than teams without.
As I said in this post teams with a high differential between O NY/A and D NY/A are more likely to have a winning schedule than teams that don’t. The Cowboys, last year and in past years, have had an offense which averages in the top 10 in O NY/A (Jason Garrett is a great offensive coach, but that’s a different story.) They need to increase their defensive NY/A in order to get to the next step. The way to do that is to maintain/increase sack level, and decrease completed passes against us. In order to do this we must get better corners, like ScarletO said, and increase the number of QB hits and pressures against the opposing QB. So, to quote Maverick, ScarletO, I’m not disagreeing with you, I’m really just agreeing with you in a confused, roundabout way. Just don’t discount the power of the pass rusher.
Another user-created commentary provided by a BTB reader.