Is Harris one of the league's top cover corners, or a product of the system in which he plays? Cian Fahey says the answer lies somewhere in the middle.
13 Jun 2013
by Tom Gower
One of the tables you will see in Football Outsiders Almanac 2013 is performance based on most common personnel groups. We do this for each team and the opponents it faced. From this, you can get a good general picture of how a team played and how teams matched up to them. The limitations of space, though, don’t permit us to go into detail on particular matchups.
For 29 of the 32 teams, the most common offensive personnel grouping in 2012 was 11 personnel: one running back, one tight end, and three wide receivers. (The exceptions were Detroit, Houston, and San Francisco.) When researching the Texans this offseason for FOA 2013, one thing I discovered is that they played in base defensive personnel (with four defensive backs) 16 percent of the time against offensive 11 personnel in 2012. That was down from 27 percent in 2011. Staying in base personnel 27 percent of the time seemed like a lot to me, but I was not sure just how much it was relative to the rest of the league.
After running the numbers, it was indeed an awful, awful lot of the time. Even that reduced figure of 16 percent meant the Texans were in base personnel more than any defense in 2012 team save two. Here’s how often each team played in base personnel on defense against offensive 11 personnel the past two seasons.
|Defensive Base Personnel vs. Offensive 11 Personnel, 2011-2012|
As you can see, in the past two years only the 2011 Panthers used base defensive personnel against 11 personnel more than the 2011 Texans did. In 2012, the Steelers led the league in how often they played base personnel against 11 personnel, and even they were in their sub package four-fifths of the time.
It is also immediately clear from the table that the Texans were not alone in playing more defensive backs against 11 personnel in 2012. In all, 28 of the 32 teams played base personnel less often, with the Panthers going from doing so over a third of the time to doing so hardly at all. Of the teams that increased how often they played base, the Eagles still ranked in the bottom five in how often they used four defensive backs. The Rams surprised me. They actually had healthy cornerbacks, Cortland Finnegan is relatively stout in the slot, and they drafted Alec Ogletree in the first round because they did not have a good cover outside linebacker, but that may just be Jeff Fisher's preference. I do not have anything on the Redskins or Seahawks; reader explanations are invited.
Fine. If teams are not playing with four defensive backs against 11 personnel, then how many are they playing? Unless you’re the Chiefs or Texans, the answer most of the time is five. Here are the full 2012 numbers for the most frequent sub package formation each team used, how often they used that many defensive backs, yards per play allowed, success rate (from the defensive perspective, so greater is better), and defensive DVOA.
|Team||DBs||Freq||Yards per Play||Success %||DVOA||Team||DBs||Freq||Yards per Play||Success %||DVOA|
The frequency column shows that most teams picked their preferred sub package and stuck with it. On average, they used it roughly 81 percent of the time. The Packers were the only team that showed a real split in how often they were in which package, using five defensive backs 51 percent of the time and six defensive backs 44 percent of the time. We only charted them with six snaps using their base 3-4 look against 11 personnel. Most teams were more divided between dime and base as their primary alternatives to the nickel they overwhelmingly preferred.
What does this all mean? To me, the most interesting thing in these tables is the apparent change in strategic preferences of having more defensive backs on the field. It does not seem to have been driven by necessity. Here is how teams did against 11 with a given number of defensive backs on the field in 2011.
|DBs||Freq||Yards per Play||Success %||DVOA|
If there was a reason to play more defensive backs based on these numbers, the jump is not going from base personnel to nickel, but instead to playing seven defensive backs. That is such a small percentage of snaps, though, that it is hard to draw any conclusions off of. The other numbers in the chart indicate that teams were not clearly better off playing base or nickel or dime.
Now, here is what happened in 2012.
|DBs||Freq||Yards per Play||Success %||DVOA|
As teams shifted from playing base personnel to nickel, defenses got slightly better in base personnel and slightly worse in nickel. The results when playing with seven defensive backs stand out again, though this time in the other direction. Again, the sample is too small to draw any particular conclusions. Looking just at having four to six defensive backs on the field, defenses as a whole performed slightly worse in 2012 than they did in 2011 as DVOA declined from 0.2% to 2.9% (defense, so larger numbers are worse). NFL defensive coordinators do not appear to have solved 11 personnel yet, though at least they haven't made the problem worse.
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