Bills Move to No. 1 in DVOA with Dominating Defense
NFL Week 4 - We have a new No. 1 team in DVOA this week, the Buffalo Bills, and they are No. 1 in DVOA by a hefty margin after putting up one of the biggest games in DVOA history with their 40-0 shellacking of Davis Mills and the Houston Texans. There's a gap of over 16 percentage points between Buffalo and our No. 2 team right now, the Dallas Cowboys. The undefeated Arizona Cardinals are right behind in third place, followed by Cleveland, the Los Angeles Rams, and Baltimore.
But the Bills are the big story, and we've got a lot of fun data to share about the incredible defensive performance they put together on Sunday. Right now, with the current opponent adjustments, the Bills come out with -134.4% defensive DVOA for Sunday's win. That would be the best defensive performance in a single game ever measured by DVOA, going all the way back to 1983.
OK, you are probably thinking, but that's only with early-season opponent adjustments. Regular readers know that early in the season, we don't do our opponent adjustments at full strength. Right now, they are only at 40% strength because we don't truly know yet how good teams are. Certainly once the opponent adjustments are stronger, Buffalo's rating for this game will be less impressive, right?
Don't be so sure. The opponent adjustment for playing against Houston may not be as strong as you think. Some of that is due to the specifics of how our system works. The opponent adjustment will be based on how Houston's offense plays for the entire season, and that will include a few games of Tyrod Taylor at quarterback. But Davis Mills also may not be as bad as he looked on Sunday. Houston's pass offense DVOA was -2.0% against Carolina the week before, far from the worst in the league.
I was curious what would happen to Buffalo's defensive rating for this game with opponent adjustments at full strength, so I ran a set of DVOA ratings with those adjustments. And it turns out Buffalo's defensive performance in this game falls from the best ever to ... still the best ever, just by a smaller amount! Buffalo would be at -127.2% DVOA with full opponent adjustments. Here's a look at the best single defensive games in DVOA history. I'm listing Buffalo's rating with the full opponent adjustment, but of course that rating is subject to change over the course of the entire season as we gather more data on both Houston and Houston's other defensive opponents.
|Top Single Games by Defensive DVOA, 1983-2021|
Buffalo's defensive performance might be even more impressive if we only look at pass defense DVOA, although it is no longer the best game ever measured. Buffalo's pass defense DVOA is -208.4% with the current opponent adjustments and would be -204.7% with full opponent adjustments. Mills had just 87 yards on 21 passes that included four interceptions. He had a fumble on a sack which Houston recovered, plus Jordan Akins fumbled after a reception. Buffalo's pass defense DVOA for this game is actually better than what the New Orleans Saints put up last year when they played against a Denver team that had no real quarterback!
|Top Single Games by Pass Defense DVOA, 1983-2021|
As an aside, we could also look at these stats from Houston's perspective and get similar lists, but today I wanted to concentrate on the Bills defense. It will be fun to see where this game stands from Houston's perspective when we get to the end of the year and we know how well Buffalo's defense has played against other opponents.
Also, how crazy is it that two of the teams with the best pass defense ever recorded in a game lost those games?
Here's another list. Buffalo's defensive performance was so strong against Houston that the Bills also break into the list of the ten best overall games in DVOA history. Once again, the ratings I'm listing here are the ratings with full opponent adjustments applied, subject to change over the rest of the season.
|Top Single Games by Total DVOA, 1983-2021|
When you have a game this strong and it counts as one of just four games in the current sample, it's no surprise to see the team involved moving into the No. 1 spot in DVOA overall. The surprise might be the way that Buffalo's defense is so outplaying its offense so far this season. The Bills offense ranks just 16th in DVOA through four weeks, with positive ratings only in Weeks 3 and 4. Buffalo is second in the league in scoring because the defense keeps putting the offense in great field position. Buffalo starts its average offensive drive at the 35.9-yard line, the best figure in the league by a signficant margin. The Bills are also second in the league with 46 offensive drives because the defense keeps getting them the ball back.
Although Week 4 was by far their best game, the Buffalo defense has been better than average in all four games so far this season, and so they also have one of the best defenses ever tracked through four games of the season.
|Best Defensive DVOA
Through 4 Games, 1983-2021
What's most remarkable may not be how good the Buffalo defense has been through four games but how big the gap is between Buffalo and the rest of the league. Right now, the No. 2 defense in DVOA is New Orleans -- surprising given that Daniel Jones led the league in passing DYAR this week playing against the Saints. But the Saints were good enough in their first three games, especially against the Packers in Week 1, to still rank second in defensive DVOA. The Saints are at -18.4% defensive DVOA right now. This means the gap between the Bills and the Saints is more than 30 percentage points! As you can probably imagine, this is the largest gap between the No. 1 and No. 2 defense ever recorded after four weeks of a season.
|Largest Gap Between Top 2 Defenses After Week 4, 1983-2021|
|Year||No. 1 Def||DVOA||No. 2 Def||DVOA||Gap|
Now, here's the downside for Buffalo: we know that defensive performance tends to be more variable than offensive performance, and the power of regression to the mean is stronger. If we want a reminder that great defensive performance doesn't always continue for the entire season, we only have to remember back to the New England Patriots of two years ago. It's possible that our opponent adjustments just aren't correcting enough for the value of playing against a series of young and/or backup quarterbacks. It would be better for the Bills if their offense was ranked first and their defense was 16th. However, based on our preseason projections and how good their offense was last year, there's a strong chance that the Buffalo offense will be better than this for the rest of the season. So even if the defense does come back to earth -- and it will -- the Bills are still set up to be a top Super Bowl contender.
This all sets up for an awesome Sunday night game this weekend, because our best defense is going to be playing our best offense, the Kansas City Chiefs. Although the Chiefs' offense is not quite as impressive as the Bills defense right now, it's still very impressive. The Chiefs are No. 1 on offense at 41.1%, with no other offense above 30%. Kansas City has the 14th-best offense we've ever tracked through four games. The problem is that their defense is almost as bad as the offense is good, easily ranking dead last so far this season.
How Good Is Arizona?
The Bills are also now No. 1 in our DAVE ratings which combine early-season DVOA with the preseason projections. However, even after four weeks, the DAVE ratings are still 70% based on those preseason projections, so the next two teams are the two teams we had on top of our preseason forecast, Kansas City and Tampa Bay. Arizona fans might be annoyed to see the Cardinals down at No. 10 in DAVE even though they are the final unbeaten team in the NFL this season. Our preseason projection for the Cardinals had them as a league-average team, or very close to it. How likely is it that we were totally wrong about them?
The ratio of DVOA to projection used in DAVE is based on looking at what ratio best predicts DVOA over the rest of the season, but it's certainly possible that we've painted with too broad a brush. Perhaps things are different if we specifically look at teams that had average DVOA projections and then way outplayed those projections in the first four weeks? I went and looked at all teams with a projection between -5.0% and 5.0%, going back to 2010. Here's a look at the teams that most outplayed their projections in Weeks 1-4, and then what the final DVOA ratings were for those teams.
|Biggest Outperformance of an Average
Preseason DVOA Projection After Week 4, 2010-2021
|Only includes teams with projection from -5.0% to 5.0%.|
What can we learn from this table? I went to 13 teams and included the 2015 Falcons to point out that sometimes hot early teams really crash out. But overall... I guess it looks like these early strong performers are more likely to keep at a high level all year than DAVE might otherwise indicate. Five of them were very strong for the rest of the year, six if you want to count the 2010 Jets. These teams had an average DAVE of 9.0% after four weeks, but their final actual DVOA averaged 15.0%. So for these teams, the early performance meant a little bit more than it did for the entire sample of teams from 2010-2019 that I used last year to create the new DAVE ratios. Perhaps that's a good sign that the Cardinals can continue outperforming their mediocre preseason projection.
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Here is the Football Outsiders Top 16 through four weeks of 2021, measured by our proprietary Defense-adjusted Value Over Average (DVOA) system that breaks down every single play and compares a team's performance to the league average based on situation in order to determine value over average. (Explained further here.)
OFFENSE and DEFENSE DVOA are adjusted for opponent and performance indoors and consider all fumbles, kept or lost, as equal value. Because it is early in the season, opponent adjustments are currently at 40% strength. SPECIAL TEAMS DVOA is adjusted for type of stadium (warm, cold, dome, Denver) and week of season. As always, positive numbers represent more points so DEFENSE is better when it is NEGATIVE.
DAVE is a formula which combines our preseason forecast with current DVOA to get a more accurate projection of how a team will play the rest of the season. DAVE is currently 70% preseason forecast and 30% actual performance. It is not currently adjusted for any backup quarterbacks.
To save people some time, please use the following format for all complaints:
<team> is clearly ranked <too high/too low> because <reason unrelated to DVOA>. <subjective ranking system> is way better than this. <unrelated team-supporting or -denigrating comment, preferably with poor spelling and/or chat-acceptable spelling>
Click here for the full table.