NFL offenses and defenses are not mirror images of each other. The gap between the best and worst offenses is generally bigger than the spread on the defensive side of the ball. And strength of schedule is more likely to play a key role when it comes to determine the best and worst defenses, too. Today’s post is a two-parter: in Part I, we look at some data on the best and worst teams in the modern era, while Part II analyzes the above claims.
Ranking offenses (or defenses) isn’t easy. I don’t like using yards, which is misleading in a lot of ways. Points scored sounds good, but non-offensive scores and other big plays on defense and special teams can make that metric less telling. There are some very good advanced metrics, but they don’t help us if we want to go back to the 1970s. So I simply used offensive touchdowns scored to rank the offenses and offensive touchdowns allowed to rank the defenses. And since I’m going to go back to 1970, I’ll be comparing each unit to the league average in that season.
Part I – Team Rankings
In addition, I’m going to adjust the offenses and defenses for strength of schedule. I’ll be doing this in an iterative way just like I do with the SRS. Listed below are the top 100 teams since 1970 in terms of offensive touchdowns per game over average (and in addition to adjusting for strength of schedule, I’ve pro-rated the non-16 game seasons to 16 games). The first line shows the 2007 Patriots, who scored 67 offensive touchdowns when the league average was 34.6. Therefore, NE gets credit for being 32.4 touchdowns over average. The Patriots’ schedule was actually difficult (once you adjust for the fact that their opponents faced New England) — it cost the offense nearly 2 touchdowns — so their final rating is +34.4.
[table id=201 /]
Seeing the ’75 Bills on there was a little shocking to me,, but Buffalo led the league in passing touchdowns, points, yards and rushing yards and ranked 3rd in rushing touchdowns, against a difficult schedule in a defensive era. The 1999 Rams were 21.8 touchdowns over average on offense, but they faced an absurdly easy schedule, one them gave them approximately 6 extra touchdowns. In fact, the three most offense-friendly schedules since 1970 belong to the ’99 Rams, ’72 Dolphins and ’82 49ers. Seven of Peyton Manning’s Colts teams are on there, including an incredible five-year stretch beginning in 2003. The 2009 and 2010 Patriots faced two of the hardest schedules since the merger among elite offenses.
We can also look at the worst 100 offenses:
[table id=202 /]
In the dominant offensive environment of 2011, five teams slipped well below the average: Indianapolis, Cleveland, Jacksonville, St. Louis and Kansas City. The worst three offenses were the Marc Bulger/Kyle Boller/Keith Null 1-15 Rams from 2009, the Andrew Walter-led Raiders, and the sophomore version of the ‘Yucs. It is amazing that the 2004 Bears ranked last in both points and yards despite facing one of the weakest slate of defenses that you’ll ever see.
What about the top defenses? I’m grading defenses by touchdowns allowed under average, but to be consistent with the above, a positive number is a good thing in both cases: a higher number means more touchdowns allowed under average and a higher number means a more difficult schedule (i.e., faced more good offenses):
In the case of the Steelers and the Bears, it’s not their championship defenses that rank first. In Pittsburgh, the ’76 Steelers had one of the most dominant nine-game stretches ever, and allowed only one touchdown per game despite facing a difficult schedule. The ’86 Bears not only allowed fewer points than the ’85 version, but they had a significant edge in touchdowns allowed, although much of that is explained by strength of schedule.
Comparing two of the best modern defenses reveals some interesting results. The 2000 Ravens had a really easy schedule, playing some particularly anemic offenses. The Ravens rank 8th in offensive touchdowns allowed if you remove SOS and the 2002 Bucs rank 5th; once you adjust for SOS, Tampa Bay drops only one spot while Baltimore falls all the way down to 29.
The easiest SOS any defense faced since 1970? That would be the slate of opponents the 1979 Buccaneers played; the average offense was 6.6 touchdowns below average, which helped Tampa Bay post some unbelievable defensive numbers that season. The 1998 Arizona Cardinals, often mentioned as the worst playoff team ever, faced the second worst group of offenses (-6.5).
What about the worst 100 defenses?
The 1981 Colts allowed an incredible 67 offensive touchdowns, putting them a distant last in the group. Also in the bottom 10: the 2011 Bucs that basically quit for the last 10 games and the 0-16 2008 Detroit Lions.
But I don’t just want to look at lists today. Which brings us to…
Part II – Analysis of OTDs and DTDs and SOS
In general, the elite offenses are farther away from average than the elite defenses. In other words, the best offenses are better at offenses than the best defenses are at defense.1 The same is true when you look at strength of schedule. For offenses — because defenses are more tightly packed — the spread on the strength of schedule numbers is smaller.2 Both of those factors combine to make offensive rankings less susceptible to SOS adjustments than defensive rankings.
I looked at the top and bottom 100 offenses in non-SOS adjusted offensive touchdowns over average and noted how they performed the next year. The top 100 offenses, on average, were 17.4 touchdowns over average and had an SOS of -0.6; the next season, those offenses averaged 9.3 touchdowns over average. The bottom 100 offenses were 14.2 touchdowns below average, faced a schedule that was +0.4 touchdowns harder than average, and were 5.3 touchdowns below average the next season.
The two key takeaways: strength of schedule had a pretty minimal effect for those extreme teams and there was significant but not overwhelming regression.
The top 100 defenses (again, not adjusting for SOS) allowed 12.8 fewer touchdowns than average and had a slightly easier (-0.5) schedule than average. But the next season, they were only 4.5 touchdowns below average. The worst 100 defenses were 14.9 touchdowns worse than average and had a slightly harder (+0.8) schedule than average. In Year N+1, they were only 4.8 touchdowns below average.
So the best offenses (+17.4) were better than the best defenses (+12.8) and regressed by significantly less than next season (+9.3 vs. +4.5). This is one of the reasons that having a great offense is better for the long-term health of a franchise than having a great defense. The correlation coefficient between Year N TDabAVG and Year N+1 TDabAVG was 0.47, while the CC between those variables on the defensive side of the ball was 0.35. The correlation coefficient between (unadjusted) Year N TDabAVG and Year N SOS was -0.10 for the offense (the weaker the SOS, the better the production) and -0.17 on defense. While not significant, this does indicate that strength of schedule has a larger impact on defensive numbers than offensive production.
- Since 1970, 61 teams have averaged one more offensive touchdown per game than average and 33 teams have averaged at least one fewer offensive touchdown per game than average. On the other side, only 15 defenses have prevented opponents from even getting within one offensive touchdown per game of league average, while 38 defenses have allowed over 1 touchdown per game more than average. It’s very, very difficult to be so dominant defensively, but we see dominant offenses (even when compared to league average) four times as often. The standard deviation in offensive touchdowns per game is 0.54 compared to 0.47 for offensive touchdowns allowed. [↩]
- For example, only 23 teams faced defenses that allowed 0.25 (or fewer) fewer touchdowns per game than average, while 39 teams faced offenses that were, on average, 0.25 or more touchdowns per game better than average. Similarly, only 25 offenses had schedules that were really easy (0.25 touchdowns per game above average allowed) while 41 defenses faced really easy schedules. [↩]