Today’s guest post/contest comes from Thomas McDermott, a licensed land surveyor in the State of California, a music theory instructor at Loyola Marymount University, and an NFL history enthusiast. As always, we thank him for his hard work.

In a previous post, I provided SRS-style ratings for all offenses since 1970, using only points scored by the actual offense (including field goals). Today, I’ll do the same thing for defenses – meaning, of course, our “metric” will be points allowed only by the actual defense. ^[1]To quickly recap: SRS ratings for offense (OSRS) and defense (DSRS) on PFR’s website include points scored by the defense and special teams. To get a more accurate points-based evaluation of … Continue reading

Here’s how to read the table below: in 1970, the Vikings allowed 10.2 points per game, 8.2 of which came from touchdowns and field goals allowed by the defense. This leaves 2.0 PPG scored by their opponent’s defense or special teams (i.e., due to Minnesota’s offense or special teams). ^[2]In this case, it was the result of three touchdowns off of offensive turnovers and one on special teams, as highlighted by Chase in this post on estimated points allowed per drive. Their 8.2 Def PA/G was 9.5 points better than league average; after adjusting for strength of opponent, their rating remains at 9.5. Their overall points allowed SRS rating (DSRS) is 9.2, meaning PFR’s defensive SRS rating undersells them by 0.3 points.

As was the case when we looked at the offensive ratings, there’s not too much change near the top when we switch from PFR DSRS to True D SRS; the names we’re accustomed to seeing shift around a bit, but basically remain within the top 15. This makes sense: as stated in the previous post, special teams/defensive points scored only make up about 8% of the total points scored by a team. I was struck by one defense in particular that ended up at #3 when we remove these “non-offense” scores – the 2009 Jets.

Some brief thoughts on the 2009 Jets Defense:

I was somewhat surprised to see the Jets ranked so high. Admittedly, I didn’t follow the NFL very closely back then (meaning, I wasn’t looking at stats, etc.), but also, I don’t recall ever seeing their name come up in any GOAT lists. ^[3]I did some quick research online and only found a few Jets-specific (fan related) articles that discuss the defense in a historical context (here and here). Rex Ryan actually recently compared this … Continue reading In any event, by this metric, they are the third best (regular season) defense since the merger, in the same company as the 1970 Vikings, the 2002 Bucs and the 1985 Bears. If this is common knowledge to the readers of this site – that the 2009 Jets are in the discussion as one of the greatest (again, regular season) defenses of all time – then my apologies, but I felt that they deserve a closer look:

• For starters, any discussion of points allowed has to take into account the 49 special teams/defensive points the Jets gave up in 2009. That’s a lot of points – it’s tied for 15^th place among 1105 teams since the league went to a 16-game format in 1978. After stripping those away, we see their actual defense only allowed 11.7 PPG (187 total), which is ranked 22^nd since the merger. After era adjustment, they jump 12 spots to 10^th (8.2 Def PA/G OvAvg). So without any SOS adjustment, this defense is Top 10 since the merger – just under the mythical 1985 Bears and ahead of the (recently mythical) Legion of Boom 2013 Seahawks. ^[4]Yep, I’m aware those two teams won Super Bowls, and I also believe that that fact should be in the discussion. But this post is just covering the regular season and this specific metric; it’s not … Continue reading

• After adjusting every team for strength of opponent, the Jets land at #3 (just edging out the ’85 Bears at #4). This gives them a SOS of +0.9, which isn’t a whole lot, ^[5]The SOS of +0.9 “feels” right. They faced some great offenses – New Orleans (9.2 Off PF SRS), the Pats twice (7.1) and Indy (5.0) – but they also feasted on some bad ones: the Raiders (-7.1), … Continue reading but it is pretty good for the Top 10 – only the 1977 Broncos had a tougher schedule (a lot tougher, +2.5). What really puts them up there though, are the other teams with easy schedules dropping: the 2000 Ravens and the 1975 Rams both drop to 13 and 16 respectively.

• Moving off of this post’s specific metric, but still related, are shutouts. The Jets had two shutouts, but not against good offenses – Oakland and Cincinnati – and this really isn’t a big deal anyway since 58 other defenses have done this since the merger (the NFL record is the 1976 Steelers with 5). But a shutout means not allowing a team to score ANY points, including those pesky “non-offense” points. ^[6]There’s surely an argument to be made that some special teams failures, as in allowing a punt return TD, are “defensive” failures, and perhaps worth looking at in the future. In any event … Continue reading What if we just looked at passing and rushing touchdowns allowed? The Jets do pretty well here: in 6 games the Jets defense did not allow a single rushing or passing touchdown. That’s tied for third in the league since the merger (9 other teams have done it), only 4 other teams have more than 6 “offensive touchdown shutout” games: the 1976 Steelers with 8, ^[7]This happened during probably the greatest defensive 9-game run in history (a category that I just made up): in weeks 6 through 14 of the 1976 seasons, the Steelers gave up a total of 28 points (3.1 … Continue reading and the ’70 Vikings, ’72 Steelers and ’91 Saints each with 7.

There’s a lot of other ways to evaluate defenses – yards, DVOA, talent level (I haven’t mentioned Darrelle Revis, etc.), #RINGZ, etc. – but if we stick with points (and the regular season), the 2009 Jets defense is historically great, maybe more so than they’re given credit for.

To conclude this two-part series, below is a table with ratings for both offense and defense (sorted initially by overall SRS):

(Keep in mind that the SpD column is not any kind of special teams rating, it’s just what’s left over when the offense and defense ratings are subtracted from the total SRS).

Some quick thoughts on the whole exercise:

What I like: Seeing the “true” offensive and defensive ratings. As stated before, the special teams/defense points are usually negligible, but as we’ve seen with some teams (2013 Chiefs, 1998 Seahawks), they can greatly affect our points-based evaluation of a team. At a glance, we can see which teams might be better on offense or defense than the points would otherwise suggest.

What I don’t like: Splitting the SRS rating up into three parts – Off, Def, SpD – wrecks the elegant simplicity (and duality) of OSRS and DSRS. When looking at the ratings on PFR’s site, we get an immediate, big picture understanding of a team’s strength and balance. Seeing large numbers in the “SpD Diff” column in my list above perhaps gives the impression that special teams and “fluky” defensive scores are doing the heavy lifting for a team when we know they’re not: the percentage of plays that generate those points are miniscule compared to the number of plays on offense and defense.

Comments welcome, thanks for reading.