Blitzes are glitzy plays. Fans love it when teams blitz, but blitzes are often dangerous gambles. Send the house and hope your secondary can hold on long enough for your rushers to reach the quarterback. Ideally, your team doesn't need to blitz to get to the quarterback, and the best defenses tend to be those that can create significant pressure rushing just their front four.
We run a 4-3 under defense but with a twist, playing something like a 3-4/4-3 under hybrid, with two big guys playing two-gap and commanding double teams and the other two ideally shooting gaps to get to the quarterback. On paper, it has a lot of obvious weaknesses. The unbalanced line should be sensitive to running over the Leo end (it wasn't for most of the year), and the specialization means you depend mostly on one end to get sacks. We lined up Chris Clemons along with Raheem Brock on the field as DEs quite a lot, but this was after Red Bryant went down and the Kentwan Balmer experiment was going nowhere.
Another point of criticism is the position needs blitzes to accrue sacks. Is that true? Harder to tell. Sacks are a really limited way to tally pressure, since pressure turns to sacks incidentally based on the QB's pocket skills, the skills of your fellow rushers and the coverage skills of your own secondary. Clemons produced 7 of 11 sacks in the blitz, Brock only 1 of 9. Again, hard to extrapolate much from since sacks are such a limited stat. Football Outsider's hurry charting puts Chris Clemons at 28 pressures and Raheem Brock at 19 pressures. How many of those came out of the blitz? I have no idea. They're good numbers though. Pressures show rushing skills better than sacks do, Julius Peppers having 30 pressures over the year, Mario Williams 35 and Chris Long 43, all excellent pass rushers who you could overlook because they don't have a lot of sacks.
Clemons and Brock produced pressure out of their specialized roles. That's nice but doesn't necessarily improve your defense, not if to get those stats you need to blitz a lot. Clemons needed a lot of blitzing to get sacks, does that mean our system needed a lot of blitzing to get to the quarterback? ESPN's numbers say "not really". We rushed 5+ less frequently than the Rams and Cardinals (but more frequently than the best defense of the division, the 49ers, we're at about league average in blitzing frequency). The sack rate jumped but the sack rate always jumps when you blitz, the more important numbers are that 16 sacks came from rushing four or less (12 of those from Brock/Clemons), and 21 from rushing five or more (8 of those from Brock/Clemons). That's not a noteworthy jump, and it's similar (if on a much lower level) to the output of the Steelers when you compare their blitz to their 4-man rush, a doubling of sack rate but not a big jump in total sacks. So, fairly typical, which is not what I expected. It seemed to me when watching the Seahawks all of last season that we relied on the blitz quite heavily for pressure, yet the stats say otherwise, perhaps partially due to our more traditional formation with both Brock and Clemons on the field in the final handful of games.
What is worrisome is how the interception rate falls in the five-man rush, which shows you're trading getting to the quarterback for giving your secondary a chance at the ball. The overall improvement in defensive performance against passing when blitzing is not too noteworthy. These stats tell us the Seahawks do not need to blitz to get to the quarterback overall, which tells us a bit more about Clemons' role in this scheme and his weaknesses. He needs to be freed to reach the quarterback, but we can reach the quarterback when he is getting blocked out of the play.
I'm not a huge fan or a big critic of this scheme. I think Clemons and Brock's production is largely scheme-based and we need a big talent upgrade on the front four before the scheme can truly be put to the test (or abandoned, depending on PC's preferences). One thing I do like is how creative PC gets with multi-DB packages and blitzing from the secondary, noticeably sending Lawyer Milloy (4 sacks, 6 pressures) and Jordan Babineaux (1.5 sacks, 7 pressures). This is less the case on 1st and 10, but I think further numbers from ESPN should show how important the secondary blitz is to our scheme.
Don't be fooled into thinking our blitz formations necessarily have much to do with our basic 4-3 under and its unbalanced line, as we often blitzed out of the bandit or similarly weird formations. Take this one, 3rd and 8 from the San Fran 15:
The Seahawks have seven men threatening the line: Jordan Babineaux, Raheem Brock, Aaron Curry, Brandon Mebane, Lofa Tatupu, Chris Clemons and Roy Lewis. The down linemen are Brock, Curry, Mebane and Clemons, showing very little relation to our base formation. At the snap, Babineaux and Lewis drop back while Tatupu joins the down linemen in rushing the passer. Tatupu is picked up by the running back, and the blitz/offensive confusion frees up Clemons to go one-on-one with Barry Sims and Curry one-on-one with Chilo Rachal. Both beat their men very quickly and combine to sack Alex Smith for a loss of 10. It's good, it works, and regardless of how our line develops, I think our more creative blitzes will remain key to our defensive formation, both secondary blitzes, formations with two leo ends (though the frequency of these should lessen if Red Bryant is in for all games), and in the form of Aaron Curry blitzing inside, as he's a force at that role (3.5 sacks and 12 pressures over the season, none of the sacks coming from the Sam position).