After last season, the defense has come under a lot of scrutiny on this site (and everywhere else for that matter), most recently on the excellent Food For Thought piece by ScarletO which I trust you've all read. And that got me thinking about where it all went wrong. To figure that out, I had to start at the beginning.

To paraphrase a little: "In the beginning, Jerry hired Wade Philips. And the defense was without form, and void; and darkness was upon the face of the defense. And Wade moved upon the face of the defense. And Wade said, let there be sacks."

Obviously Jerry hired Wade in large part  on the strength of his record as DC in San Diego, expecting a similar performance in Dallas on a defense that in 2006 ranked 20th in Sacks, YPP, PA, DPR and 13th in yards allowed. How did that turn out?

Defensive Stats San Diego 05-06 & DAL 07-08

Looking at the first three columns, it looks like Wade got the D back on track in a hurry. The SD and Dallas numbers are virtually identical, and way too close to be mere coincidence. Wade's defensive philosophy is much more than a simple 3-4, it's all about pressuring the QB to create defensive plays with zone blitzes, even on 1st downs, pressure packages from different angles and all sorts of other weird stunts (see Dave's recent piece on the 46 Defense) that will get you sacks as if they were being offered up at a firesale. Now this type of play can result in the secondary getting burned for big plays on occasion, but over four quarters, Wade's defenses usually make more game-changing plays and let their offense get back in the game. In San Diego this, in part, led to a 14-2 record in his last season as DC.

The last three columns however paint a very different and agonizing picture. If everything had been going right with this defense, we should have been much closer to the stats posted by San Diego in 06, and possibly closer to their 14-2 record as well. But that didn't happen. So what went wrong?

Part of it may have been due to Wade now being the HC and not the DC. Brandon Worley made a convincing case here that the defense had significantly improved after Wade took over play calling duties. Alas, that was posted early December last year, before the Baltimore and Philly games, so the jury may still be out on that.

The other part of the explanation must have to do with the secondary. Getting a boatload of sacks doesn't always mean you're the best defense, but pressuring the QB and flushing him out of the pocket should in principle benefit your secondary. Most quarterbacks are not as great on the run as they are in the pocket, which should cause more incompletions, sacks, interceptions, and most importantly, should get the opposing teams' offense off of the field. Judging by the numbers above, that didn't happen with our secondary.

The Secondary

Assessing the statistical performance of the secondary is tricky, and some of the more traditional stats bandied about are eye candy devoid of any nourishing insight.

Tackles Total, Solo or Assisted mean jack for the secondary performance, because they could mean anything. Did a CB tackle a WR or a RB? Did he tackle a WR because he failed to break up a pass thrown into his area? Did the tackle come on a Blitz? Questions, questions ...

Passes Defended? As an absolute number, useless. You need to normalize it against something, e.g. passes thrown against the CB/Safety etc.

Also, as I have no clue how to assess the secondary against the run, I'll concentrate in the following only on the performance against the passing game. Raf has made a lot of very good posts on the secondary - I believe it must be a topic very close to his heart - here and here and here ... and I highly recommend you look up these and more if you want to dig deeper. The raw data for the table below was taken from ProFootballFocus.com, combined with some Excel wizardry and painstakingly entered into html tables. The data available at that site are not official NFL stats, it seems there's a bunch of people there reviewing every single game film to get at these numbers, so I'm not sure that they're 100% accurate, but am sure they are good enough to make a solid point - and the data is free.

To create the following table, I have combined the stats for each individual NFL CB and Safety ("The Secondary") and summarized it into the following team table.

2008 Secondary Coverage Stats

TA: Thrown AT; %PD/TA: Passes Defensed in % TA; DPR: Defensive Passer Rating

How do these stats fit with a Defense that ranked 8th overall in yards allowed? Obviously, the secondary in 2008 was marred by injuries, suspensions and age catching up with some players, which obviously impacted our secondary performance. Equally importan however, opposing teams consistently found weaknesses in our coverage to exploit, and while the secondary weren't allowing too many big plays, they were hurt with short and intermediate throws.

Now it is worth noting that Wade's defenses never racked up an overly impressive number of interceptions, so even with an improved secondary  in 09, I wouldn't look for Dallas to crack the Top 10 in interceptions even though some of our rookies were fiendish interception machines in college. You just won't see a lot of QB's under pressure going for the long ball (with a higher chance to be picked off), instead they're much more likely to go for the short, safe throw that keeps the drive alive.

A further breakdown of coverage stats by position shows that the CBs had a combined DPR of 89.1, ranking them 19th in the league. The safeties had a combined DPR of 122.6, ranking them 30th in the league. Of note, the stats show only 54 TAs for safeties. Gerald Sensabaugh had 41 TAs in Jacksonville and managed a 63.5 DPR. While there have been questions about his ability against the run, there is no question that he will significantly improve our coverage. But then again, Jacksonville is not exactly a pressure defense.

I wouldn't be surprised at all if Terence Newman and Ken Hamlin were the only players from last years' unit to make the starting lineup, with Orlando Scandrick losing out to Mike Jenkins. From what I've been reading here recently, it would seem that despite replacing almost half of the secondary unit, we are now in a much better position, with far better depth. Well, hope springs eternal.

Words of wisdom for Wade and Dave Campo: " If you're going to kick a tiger in the ass, you'd better have a plan for dealing with its teeth."