Introducing DVOA v6.0

by Aaron Schatz

One of this offseason's big projects at Football Outsiders was another round of improvements on our DVOA formula. Today, with the release of Football Outsiders Almanac 2009, we also switch over the stats pages on our site from the old version of DVOA to the new version.

The biggest change in DVOA v6.0 is that offense and defense are no longer judged on the same baseline. This is related to the specific adjustments and additions made to the formula, particularly these three:

1) DVOA now includes more penalties. Originally, DVOA only included passes and runs. In 2007, with DVOA v5.0, we added defensive pass interference and began to count intentional grounding with yards lost (rather than just as a regular incomplete pass.) Now, we add in the two offensive penalties which have both the highest correlation to wins and the most consistency from year-to-year: false starts and delays of game. Yes, that's right, delay of game really has a higher effect on wins and losses than holding, offensive pass interference, or any number of other penalties. DVOA only counts false starts and delays of game on offense, so fourth down delays when a team is trying to draw the defense don't count, and neither do those lame penalties for when a guy spikes the ball after the play or breathes on the official wrong or whatever.

However, there is no correlation between the defense on the field and the frequency of false starts and delays of game. Therefore, we could only count these changes on the offensive side of DVOA. That required a big change: separate baselines for offense and defense. The average for "success points" in any given situation is now lower on offense because of the possibility of a penalty. This also means that offensive plays come in three categories: instead of just rushing and passing, there are also penalties. So on defense, all pass plays and run plays from 2002-2007 total to 0% DVOA, but on offense they do not, because you have to add in false starts and delays of game (which are all negative plays) to get 0% DVOA as the average. Therefore, you may notice that team DVOA for both pass offense and run offense will seem higher than in past years. (This is not an issue with defensive pass interference or intentional grounding, since we count both of those as pass plays.)

2) Once we split offense and defense, we were able to change the way we counted aborted plays such as dropped snaps and incomplete backwards lateral passes. These plays now only count as negative for the offense, and defenses do not receive a "bonus" just because the quarterback can't hold onto the snap. Defenses still get credit for fumbles when they actually strip the ball.

3) DVOA v6.0 improves the way we adjust for teams playing from behind or with a lead in the fourth quarter. These adjustments are different for offense and defense. We also added an adjustment for the final two minutes of the first half when the offense is not near field-goal range.

Other improvements in DVOA v6.0 include:

• Red zone plays (for team DVOA) are now worth 25 percent more than other plays, rather than 20 percent.
• Offense gets a slight penalty and defense gets a slight bonus for games indoors.
• Fixes error where defensive pass interference for less than the needed yards was not getting the proper first-down bonus.
• Adds penalty for a safety, beyond just the penalty for lost yardage.

I should point out that there were also a number of adjustments that I tried but didn't include because they didn't improve the correlation of DVOA to wins in the current year or DVOA the following year. That includes adjustments based on climate rather than just indoors/outdoors, "blowout" adjustments for plays before the fourth quarter, and adjustments for home-field advantage. That last one really surprised me when it didn't actually improve correlation from year to year or from the first half of the season to the second half, but it didn't, so it doesn't go into the new DVOA.

For most teams, the new version of DVOA only makes a small change to their rating. The average team since 1995 saw its rating change by 2.7 percent. However, a handful of teams did see their ratings change significantly, and the biggest improvement belonged to a team from the 2008 season. The Jacksonville Jaguars had a total DVOA of -8.5% in the final ratings posted on FootballOutsiders.com in 2008. In the new DVOA v6.0, their total DVOA is 1.9%, more than 10 percentage points higher -- although because the old version of DVOA had a big gap between the 19th and 20th best teams of 2008, their rating actually only goes up two spots, from 22nd to 20th overall. Nonetheless, this higher DVOA rating helps to explain why our projection for Jacksonville in 2009 may be better than most fans expect.

Here's a look at which teams saw their DVOA ratings change the most with the new version of the system:

Some other changes in the new ratings that might interest you:

• The closely-packed top of the 1997 ratings [2] have shifted. The top team in 1997 is no longer Kansas City... but it isn't champion Denver either. It's now Super Bowl loser Green Bay, with Denver staying second and Kansas City dropping from first in the old DVOA to third in the new version.
• As noted in the table above, the rating for the 1999 Rams has dropped significantly. Although the Rams are still the best team in that season, they have dropped from the second best team of the DVOA Era to sixth. The all-time top five now consists of the 2007 Patriots (still the only team over 50%), 1995 49ers, 1996 Packers, 2004 Steelers, and 2004 Patriots.
• A few other champions have also dropped in DVOA. The 2000 Ravens drop from second to third, the 2003 Patriots from third to fourth (although they led the league in WEIGHTED DVOA), and the 2004 Patriots from first to second (behind the Steelers).
• The 2008 Eagles were one of the teams that got better in DVOA version 6.0, and that means that they now have one of the top ten DVOA ratings ever. Yes, even though they were just 9-6-1. Out of 38 teams with DVOA above 27.5% (going back to 1994), only two had fewer than 10 wins: the Eagles and the 2004 Buffalo Bills (9-7 with DVOA of 31.2%).
• Oh, yes, about 1994... 1994 ratings are coming soon, once I write the commentary.
• With the changes, we've also changed the special teams pages to match the way we publish the special teams numbers in the book. Special teams pages now have the "hidden" factor listed in "estimated points" as well as a measurement each year of the effect of weather and altitude on each team's special teams performance.
• All the free stats pages are now updated. Updating the Premium Database will take a little longer, mostly because the guy who handles that also handles KUBIAK and finishing up the auction functionality in KUBIAK is higher on the to-do list.
• Individual stats pages are also updated. The methods did not change, but we've done a lot to fix incorrect play-by-play from 1995-1999. Thanks to reader Jeremy Snyder for providing a ton of help in that area.

OFFENSIVE LINE STATS CHANGES

Along with the changes in DVOA, there are also a couple of changes in the offensive line/defensive front seven stats.

First, we've changed the definition of "Stuffed" to make it simpler. "Stuffed" now means exactly that -- it is simply the percentage of running back carries which are stopped at or before the line of scrimmage, no matter what the situation.

The second change is related to the increased usage of shotgun formations over the past couple years. Adjusted Line Yards are supposed to measure the quality of run-blocking. The New England Patriots led the league in ALY in 2007 and finished second in 2008, but does anyone think that the Patriots have the best run-blocking line in the league? No, part of the reason they run so well is that the defense always has to expect pass against their pass-heavy shotgun spread offense.

It turns out this is a general problem. No matter the team or the down-and-distance situation, rushing plays gain more yardage from shotgun. Obviously, the way teams defend the shotgun is leaving more room for runners, which leads us to overvalue the offensive lines.

As I said before, this shotgun advantage has nothing to do with the quality of the offensive line. As an example, here are the NON-ADJUSTED Line Yards numbers for five different offenses in 2008 -- good lines and bad ones, teams that used a lot of shotgun (Denver, New England, Kansas City) and teams that did not (New York Giants, Cincinnati).

Therefore, Adjusted Line Yards now adjust for whether a team is in shotgun or standard formation, moving offenses that use a lot of shotgun down and moving offenses that don't use a lot of shotgun up. The changes are small, but -- to give a couple examples -- the Giants pass the Patriots in last year's Adjusted Line Yards standings [3], and while the Patriots still lead the league for 2007 [4], their lead over the other teams is about one-third as large as it used to be.

There are also improvements in the way the ALY stats handle running out the clock in the fourth quarter, to match the changes in DVOA. With a fourth-quarter lead, the baseline for ALY drops each minute, starting when there are ten minutes left in the game (two-score lead) or five minutes left in the game (one-score lead). When a team is behind, the baseline goes up with each successive minute, with a steeper climb the farther the team is behind.