Statistical Review of the 2009 49ers: IX. DF7 and DBs

AUTHOR'S NOTE: If you're not already using the wide view of the site, switch to it because 2 of the tables are a little too wide for narrow view.

Welcome back for the 9th (and final) installment of my 2009 Niner stat review. If you missed Parts 1-8, you can read them here, here, here, here, here, here, here, and here.

Today in Part 9, I'll take a look at the defensive front 7 (DF7) and the secondary. To say that these units were good in 2009 would be an understatement. As I showed my overall DEF review, the 49ers' DEF ranked in the top 8 of every major statistical category provided by Football Outsiders (FO). So, there's no reason for me to rehash the same thing again in a discussion of the individual pieces of their DEF.

Rather, what I'm going to do here is take a look at how the 49ers' great DEF of 2009 was born, and what positions in particular seem to be most important for their overall defensive success. To these ends, I'll present FO's run-stopping and pass-rushing stats for the DF7, as well as DVOA stats against specific types of opposing receivers, and then relate the 2009 stats to the overall defensive performance trends of recent 49er history. From this post, we'll be able to see in a general sense what specific events seem to have had the biggest impact over time, and which players/positions seem to be the most vital.

So, let's begin...

OVERALL RUN-STOPPING STATS

Below are FO's yardage stats for the 49ers' DF7 in 2009, along with those of the average playoff OL and the Super Bowl champs' OL (Top-8 performance in bold; Bottom-8 performance in italics):

Not surprisingly, the streak continues. The DF7 was in the top 8 of all yardage-related stats except for Open Field YPC, in which they ranked 9th. This tells us that the DL was filling their gaps, the LBs were making the tackles, and the secondary wasn't allowing big gains. This last part about preventing big gains in the running game is especially important as it was what the average playoff team was best at among the stats above. Clearly, then, the 49ers currently have a playoff-caliber DF7.

After the jump, I'll finish up with the 2009 stats, and move on to a discussion of (a) how all of this defensive awesomeness came to be, and (b) what the trends mean going forward...

 Here's how the DF7 did in terms of power-running situations and tackles at or behind the line:

Finally, 2 areas in which the Niners' DEF wasn't off-the-charts awesome. However, they don't worry me so much given what the previous table showed us about the DF7's prowess within 5 yards of the line (See 1st Level). Furthermore, given that they were ranked 25th in Power Success Rate as recently as 2007, #16 represents a vast improvement.

One other thing I'll mention here is that this is the second table in a row showing that the Saints' DF7 wasn't all that good; which goes to show you that, although definitely nice, being stout up front on DEF isn't a prerequisite for championship-caliber football.

DIRECTIONAL RUN-STOPPING STATS

In terms of stopping runs in a specific direction, here's my fancy DF7 chart:

Back to our regularly scheduled program. As you can see, the Niners' DF7 was ranked among the top half of the NFL in every run direction. Worthy of note is that they were the best DF7 in the league on runs behind LT. Although it's a bit of an extrapolation, I don't think it's a coincidence that Justin Smith and Patrick Willis are over on that side of the formation.

I also have 2 other things to point out. First, the DF7's Top-10 ALY on runs up the middle seems to lend creedence to the idea - which I already discussed here - that Aubrayo Franklin had a heck of a season. Second, their #9 ALY on runs to the outside right suggests that the run DEF wasn't particularly hurt by getting only half-a-season out of run-stopper extraordinaire, Nate Clements.

More on Smith, Willis, and Clements later.

Moving on to the pass rush, below are the Niner DF7's pass-rushing stats, along with those of the average playoff DF7 and the Super Bowl champs' DF7:

After years of non-existent pressure on opposing QBs, the 49ers catapulted into the Top 3 pass-rushing DF7's in the league. And even when you remove the effect of opponent and game situation (i.e., look at unadjusted Sack Rate), they were still in the Top 10. Amazing.

OVERALL PASS-COVERAGE STATS

To wrap up the 2009-stats portion of the post, here's how efficiently the 49ers' secondary played against specific types of receivers:

I'll go backwards here a little bit. What's important to notice about the stats in this table is how the average playoff team performs. Specifically, from their rankings, it appears that pass DEF against #1 WRs, #2 WRs, and TEs was important in 2009, whereas defending an opponents' #3 (or #4) WRs and RBs wasn't all that important. From the Saints stats, it seems like covering #1 WRs and TEs was a key to their success.

With that in mind, two things. First, the Niners need a proverbial shutdown corner, stat. Although being ranked 17th isn't all that bad, the 49ers' CBs were below average against #1 WRs, and were over 15% less efficient than the average playoff team's CBs. You might ask, "But I thought they signed Clements to be their shutdown corner?" Stay tuned.

Second, the near uniformity of the evidence about covering TEs suggests that (a) it's of overlooked importance, and (b) it's a good thing SF hasn't overlooked it. For most DEFs, TE coverage is the responsibility of the strong side LB and the Ss. The 49ers are no different in this respect. Therefore, it's a testament to Manny Lawson, Dashon Goldson, and Michael Lewis that the DEF was as efficient as it was vs. TEs. It's especially impressive when you consider they had to defend 6 of the Top 13 TEs in TE DYAR (Visanthe Shiancoe, Tony Gonzalez, Dallas Clark, Owen Daniels, Jermichael Finley, and Brent Celek).

GENESIS (AND I DON'T MEAN PHIL COLLINS' BAND)

Between the overall stat review and this post, I think I've shown pretty clearly that the 49ers' DEF was about as awesome a DEF we've seen from the team in a long time. Indeed, by nearly every statistical measure provided by FO, they were among the elite defensive units in the NFL.

What strikes me about all this, however, is its abruptness. It seems like only yesterday that most of us on NN were complaining in one way or another about a lack of pass rush, a Charmin-soft pass DEF, and various players getting manhandled on the defensive front. Today, I'm talking them up like they're the next coming of the Steel Curtain. How/why did this happen?

My view is that we can trace the Niners' awesome 2009 DEF to 5 things:

1. Drafting Willis in 2007
2. Switching to a base 3-4 alignment in 2009
3. Starting Goldson at FS in 2009
4. Drafting Tarell Brown in 2007
5. Signing Dre Bly in 2009

For the rest of the post, I'll present the stats that led me to believe the above.

The "duh" entry on my list is Patrick Willis being drafted in 2007. As far as the ridiculously good run DEF goes, you can trace its beginnings to that fateful day in April. Want proof? Here's a chart showing the relationship between DF7 ALY ranking and Run DEF DVOA ranking for Niner teams from 2002-2009:

First off, you can see that the two stats basically run together, and that's to be expected. When the DF7 plays well within 10 yards of the line, odds are that the overall run DEF stats will reflect that. But, for the purposes of showing the Willis effect, you can clearly see that the upward trend begins after 2006. To add a bit more detail, check out the data points from 2006 onward. For DF7 ALY, the Niners went from 26th to 14th to 12th to 8th. Similarly, their Run DEF DVOA went from 28th to 18th to 17th to 6th. As Willis is the straw that stirs the run DEF's drink, I think it's safe to say that their awesomeness owes alot to Round 1 of the 2007 NFL Draft.

The next major contributor to the 49ers' defensive improvement was Mike Singletary's decision to scrap Mike Nolan's Big Sub, "Hybrid," or whatever-you-want-to-call-it DEF -- I call it crap -- and give the team an identity by going to a full-time base 3-4 alignment. Although it's probably affected the run DEF to a certain degree, the biggest effect of the switch was evidenced by a concomitant improvement this season in both pass rush and overall pass DEF. Here's a chart showing the relationship between DF7 ASR ranking and Pass DEF DVOA ranking for Niner teams from 2002-2009: 

Again, we have nearly a 1-to-1 correspondence, which means that recent Niner history decodes pass rush as the key to pass DEF. Indeed, just last year the 49ers' ASR was ranked 26th (!!!). Obviously, there's a chicken-and-egg thing going on wherein it may just have been the coverage letting down the pass rushers for the past 7 seasons. However, considering that both of their starting CBs missed significant playing time, it's reasonable to assume that -- in 2009 at least -- the pass-rushing chicken came before the pass-defending egg.

And if that doesn't satisfy you, here's another bit of evidence that suggests switching to the 3-4 is what underlies the pass-rush and pass-coverage improvements. Below is a chart comparing sack rates for the 11 3-4 DEFs in 2009 to those of the 21 4-3 DEFs:

From the looks of it, the 3-4 sure seems to be associated with a higher frequency of sacks on DEF. The story's the same if you look at rankings instead of the stats themselves. Specifically, the average 3-4 DEF was ranked about 6 spots higher in ASR (12.4 vs. 18.7) and about 8 spots higher in unadjusted Sack Rate (11.5 vs. 19.1).

One other thing the 3-4 did to help the pass rush, wish doesn't show up in these charts, was to get Ahmad Brooks on the field. At his size (6'3", 259), he's way to small to be a 4-3 DE, which is where the vast majority of pass rushers play in that alignment. In contrast, the majority of sacks in the 3-4 come from OLBs, a position that suited Brooks to a tee.

So, to recap, there's an inherent pass rush advantage to the 3-4, and it allowed Brooks -- who finished 2009 with 6.0 sacks -- to get on the field more because he's too small to play pass-rushing DE in a 4-3. The 49ers, who've been playing 4-3 or "crap" for the past 7 years, have been mainstays at the bottom of the ASR rankings, and - oh, by the way - the pass DEF rankings. Singletary switches to a full-time base 3-4 alignment, and - voila! - the pass rush goes from 26th to 3rd, and the pass DEF goes from 20th to 8th. Coincidence? I think not.

My final 3 reasons for SF rocketing into the defensive stratosphere are all related, and have to do with how their pass DEF DVOA relates to their ability to cover specific types of receivers. Remember that, as I showed you earlier, covering the TE seems to be really important in the NFL. And as I said, much of the responsibility for covering TEs goes to Dashon Goldson. What I'll add here is that, although covering the opposing #3 WR may not be that important for playoff participation, it's pretty darn important for the 49ers' pass DEF. Here's a chart showing the relationship between the Niners' Pass DEF DVOA ranking and their DVOA ranking vs. specific types of WRs from 2002-2009: 

In this chart, the 2 trends most correlated with the Pass DEF DVOA trend (red line) are the TE trend and the #3 WR trend. Regarding the TE trend, if it's hard to see the corresponding green line, it's because the 49ers' DVOA trend vs. TEs is almost exactly the same as that of their overall Pass DEF DVOA. In other words, if you wanted to guess the Niners' Pass DEF DVOA ranking for a given year, you'd be amazingly accurate just by knowing how they did in covering TEs. And who's responsibility is that? The strong-side LB and the FS, but the FS position seems to have had a larger effect. Back in 2002 and 2003, Zack Bronson was the FS, and he was easily the best one the Niners had prior to Goldson. In between Bronson and Goldson, they had the illustrious Ronnie Heard, the hit-heavy-but-coverage-light Keith Lewis, and the everything-light Mark Roman. During those seasons, TE coverage reached its nadir. The promotion of Goldson has taken the Niners' ranking from 27th in 2007 all the way to 6th this season.

Regarding the #3 WR trend, the 49ers have made several moves over the past 3 seasons to acquire depth in the back end of their DEF; the most influential of which have been Brown and Bly. I don't think it's a coincidence that their coverage of #3 WRs improved considerably during the season in which they signed a legit #3 corner, and in which one of their talented young backups begins to see significant playing time.

So, to recap, the 49ers' defensive resurgence in 2009 can be traced back to a structural shift to the 3-4 alignment, which put their best pass rushers in the best position (OLB), the drafting of Willis, which solidified their run DEF, and the acquisitions/lineup changes that improved their CB depth (for covering #3 WRs) as well as their coverage of TEs.

BOTTOM LINE

As this is the final installment of the series, here's what the totality of the stats say should be the 49ers' offseason focus in 2010:

1. Pass OFF!
2. Pass OFF!
3. Pass OFF!
4. Allow Alex Smith to become more comfortable in the current offensive system, and to further develop his on-field rapport with Michael Crabtree and Vernon Davis
5. Find an efficient backup RB to keep Gore healthy
6. Stop running the ball up the middle 70% of the time
7. Find a competent #3 WR
8. Find pass-protectors along the OL, rather than one-dimensional maulers
9. Leave the DEF alone!
10. Find a KR/PR

*DVOA, ALY, and ASR statistics used to produce this article were provided by Football Outsiders.