Over the last three seasons, Seattle has allowed 15.2 points per game. That’s really, really good. How good?

There are flaws with using points allowed as a measure of defensive play, of course. Seattle is known for its long drives on offense, which limits the number of possessions an opponent might have. And the Seahawks offense generally puts the team’s defense in pretty good situations. Using points allowed per drive might be preferable, or using DVOA, or EPA per drive, or a host of other metrics. And adjusting these results for strength of schedule (or, at least, removing non-offensive scores) would make sense, too.

But hey, it’s Friday, and I wanted to keep things relatively simple. ^[1]In about ten minutes, we can all have a good laugh at this line. Points allowed is a number we can all understand. Given our era of inflating offenses, it’s quite possible that Seattle’s 15.2 points per game average doesn’t stand out as particularly impressive to you. After all, the ’76 Steelers once allowed 28 points over a nine-game stretch! But consider that since 2012, the NFL average has been 22.6 points per game, which means the Seahawks have allowed 7.4 fewer points per game than the average defense.

How good is that?

In short, it depends. Do you remember the 1973-1975 Rams? Those great defenses were littered with star players like Jack Youngblood, Isiah Robertson, Merlin Olsen, Fred Dryer, and Jack Reynolds. Los Angeles went 34-8 over that period, and finished 4th, 1st, and 1st in points allowed during those three years. ^[2]Of course, Seattle has ranked 1st, 1st, and 1st. In total, the Rams allowed just 11.8 points per game during that run, while the average NFL defense allowed 20.6 points per game. So the Rams allowed 8.8 fewer points per game than the average team.

On the surface, that sounds better than these current Seahawks. And perhaps it is. But remember the picture above: what is interesting about Seattle is not just how dominant they’ve been, but how uniquely dominant they’ve been. For example, let’s create the exact same chart but for the years 1973 to 1975:

You can probably eyeball that the numbers are all lower, and maybe you can even eyeball the fact that the old Rams are farther from average than the modern Seahawks. But perhaps the most striking observation is that the 2012-2014 Seahawks just look like more of an outlier than the 1973-1975 Rams. After all, the Vikings were only 1.1 points behind Los Angeles, and the Steelers were only a half point behind the Vikings (and the Dolphins about the same behind the Steelers). Meanwhile, Seattle is 3.2 points per game ahead of its nearest competition (the 49ers), and an five points per game ahead of the third-place team, Cincinnati.

So the modern Seahawks really do look like a big outlier in their era when it comes to preventing points. There’s a statistical way to measure this, of course, using Z-Scores and standard deviations. Regular readers (or the Seahawks fans who have developed a history of frequenting this site in late January) may recall I used Z-Scores to put Seattle’s incredible pass defense last season in historical perspective. There are legitimate questions about whether this sort of data is an appropriate use of Z-scores, but we can debate that in the comments. For now, allow me to present the data. Here’s what I did:

1) Calculate the points allowed per game for each franchise for every three-year period in franchise history. ^[3]Note: I took an average of the average points allowed per game for each season, choosing to treat each season as equals, regardless of the number of games. Reasonable minds could differ on whether … Continue reading For the 2014 Seahawks, this is 15.2.

2) Calculate the average points allowed per game in the NFL (or AFL) for each 3-year period. For the 2012-2014 NFL, this is 22.6.

3) Calculate how far above or below average each defense was. For the 2014 Seahawks, this number if +7.4 (treating being below average as positive).

4) Calculate the standard deviation of points allowed per game over each three year period by each franchise. So for 2012-2014, I calculated the standard deviation of Seattle’s 15.2, San Francisco’s 18.4, Cincinnati’s 20.2, etc. For the 2012-2014 NFL, this is 2.70.

5) Divide the result in step 3 by the result in step 4 to calculate the Z-score. For the 2012-2014 Seahawks, this is +2.73, which means the Seahawks have been 2.73 standard deviations above average at preventing points.

So you know that Richard Sherman, Earl Thomas, Kam Chancellor, and the Legion of Boom are pretty good. How good? Well, that +2.73 number is the best in history. Below are the top 100 Z-scores: ^[4]Note that I did not write top 100 defenses!

There are some reasons to like this methodology, particularly in theory. Then you see results like the 2011-2013 49ers ranking 2nd, and well, it’s fair to wonder a bit about this methodology in practice. ^[5]Not to mention the first ’70s Steelers team checking in at #39, which is also only sixth best among Pittsburgh defenses!

I see no issue at all with ranking teams by the “difference” column, and well, both the 2011-2013 49ers and 2012-2014 Seahawks sneak into the top ten by that methodology. So no fancy math is needed to show that those were some dominant defenses once you adjust for era. The “quirk” that is bringing them to the top of the list is that the league-wide standard deviation in points allowed per game over trailing three-year periods has been relatively low of late; since that number is in the denominator of our Z-score, it helps San Francisco and Seattle. Is that appropriate?

That’s up to each individual reader. Here’s one more graph.  In blue, I’ve plotted the standard deviations for points allowed per game for the NFL each three-year period; as you can see, the number has been at 2.7 for the last two 3-year periods.  For reference, in orange, I’ve plotted the standard deviation among all teams in points allowed for just a single year (the last of each three year period).  As you would expect given the results of the ’73-’75 Rams and the ’12-’14 Seahawks, the standard deviation was noticeably higher in the mid-’70s than it is today.

So why did I include this last graph?

If the trend line of the blue line was consistently decreasing, this post would be taking an even more conservative tone about using Z-Scores; however, the line has been essentially flat since the late ’70s.  There’s minor variation, of course, and perhaps that variation is best to be dismissed when calculating Z-Scores (it’s why the ’93-’95 Cowboys rise to third), but 2012-2014 isn’t a particularly low period, anyway.

It’s possible that the early ’70s were somehow different — this was before free agency, which made it easier for teams to have the same roster for 3 straight years, and it was before the 1978 rules changes, which means defenses had more of an impact on the game.  What do I mean by that?  Think of the points allowed by a defense in a game as a combination of two factors: the strength of the defense and the strength of the offense. ^[6]Regular readers may recall this post on the subject, which, ironically, went back “only” to 1978. If the rules are slanted towards the offense, the number of points a team will allow will be more dependent on the quality of the offense it is facing. Which means a team’s points allowed number will be more impacted by strength of schedule than a defense in an era where the rules and the game are slanted towards the defense. In that case, a dominant defense will be dominant each week.

That’s just a theory, of course, but it’s not an unreasonable one to draw from the above chart.  So the Rams were super dominant because they were awesome, but so were the Steelers and Vikings and Dolphins, and it was an era where it was a bit easier to stand out as dominant for a long stretch of time.  It also could be related to the post-merger NFL, where a lack of parity brought high variation in strengths of schedule, which caused a high standard deviation of points allowed.  I’m just speculating here: there are all things worth investigating on another day.

But one thing we can say definitively: over the last three years, Seattle has been uniquely excellent at preventing opponents from scoring points relative to league average, and the Seahawks have been as uniquely excellent in this regard as any team over any three-year period in football history.

A fitting end to a dream season.

It almost seems silly to spend much time recapping one of the most lopsided Super Bowls ever. But we have six months until we get to watch another NFL game, so I think we can spend one more day recapping the 2013 season. One housekeeping note: Football Perspective isn’t going anywhere. Just like last year, we’ll be publishing a post every day of the offseason. So be sure to check back daily! Freelance articles are also welcome, so just send me an e-mail if you’d be interested in contributing to the site.

There were some great recaps published in the immediate hours after the Super Bowl, including summaries from Bill Barnwell and Mike Tanier, a Super Bowl edition of Audibles at the Line from Football Outsiders, Ben Stockwell’s Refocused recap at Pro Football Focus, an analytic take from Advanced NFL Stats, the gut-punching summaries from Douglas Lee  and T.J. Johnson at It’s All Over, Fat Man!, and the elated Danny Kelly and Jacson Bevens from FieldGulls.

So with 24 hours to sleep on things, here are my thoughts on how any why Seattle produced a Super Bowl blowout.

The Seattle Defense vs. The Denver Offense

I wrote a lot about Super Bowl XLVIII, but by far the most anticipated subplot was seeing Peyton Manning against Richard Sherman and the Seattle pass defense. In my Super Bowl preview, I encouraged readers to watch the YAC: No quarterback gained more yards on yards after the catch in the regular season than Manning. On a per-catch basis, Denver receivers averaged 5.75 yards after the catch according to NFLGSIS, but Seattle led the league in YAC/Catch allowed at 4.1.  The Seahawks press coverage and sure tackling seemed like a bad matchup for Denver, and it was: according to Pro Football Focus, Denver receivers gained just 3.7 yards after the catch per reception in the Super Bowl.

That’s just part of the biggest story, of course, which is how one of the greatest pass defenses in NFL history — and one of the greatest defenses in NFL history — played like it on the biggest stage. Cliff Avril (5 hurries, 2 hits according to PFF) was remarkable in the first half, dominating the Broncos offensive line and forcing both Manning interceptions. Kam Chancellor and Malcolm Smith were the recipients of both Manning picks, and both had strong all-around games, too. Richard Sherman was quiet, but Manning and the Broncos largely avoided him, which means his impact was felt.

As for the Broncos offense? Peyton Manning is the easy target, of course, and he struggled. But no offensive player wearing orange had a good game on Sunday. On the offensive line, Manuel Ramirez and Orlando Franklin in particular had terrible games, while Julius Thomas and Eric Decker were all but invisible.

Manning’s numbers were not good — he averaged 4.18 ANY/A — and even that overstates his level of production. With the deep Seattle defensive line and a dominant secondary, the Broncos offense was stuck in neutral for most of the game. The Broncos were unable to stretch the field vertically, and Seattle did the two things every defense tries to do against Manning: pressure him without blitzing and limit the yards after the catch. Whether that’s a blueprint any other team can follow remains to be seen, but the guess is “no.”

The Seattle Offense and Special Teams Outclassed Denver

As lopsided as the Seattle defense vs. the Denver offense matchup turned out to be, that was only part of the reason for the blowout victory. Percy Harvin had a big impact on the game, in the way Seattle envisioned he would when John Schneider traded a first round pick (and more) for him last April. In addition to his kickoff return touchdown to start the second half, we finally saw a glimpse of Harvin’s impact on offense. On the team’s second play from scrimmage, Harvin took a jet sweep 30 yards for a first down, and his presence seemed to open up the field for the rest of the Seahawks.

Russell Wilson played well even if he was not necessarily asked to do all that much: he finished with a 9.84 ANY/A, and his receivers had very good games. The underrated Doug Baldwin was the star with 5 catches for 66 yards and a score on 5 targets, while Jermaine Kearse was right behind him with a 4/65/1 line. Marshawn Lynch was pretty quiet — the Denver run defense was the only one of nine units to win their battle against Seattle — but it didn’t seem to matter very much.

Where They Go From Here

Pete Carroll’s team is well-positioned for a long run of success. Offensive coordinator Darrell Bevell had a shaky end to the season, but he called a good game in the Super Bowl and has proven himself as a strong coordinator. Seattle almost certainly would have lost defensive coordinator Dan Quinn, but the Seahawks run to the Super Bowl prevented him from leaving for a head coaching job. That’s a big win for Seattle, especially after having lost Gus Bradley a year ago.

The Seahawks were the second youngest team in the NFL in 2013, so the outlook is very rosy for 2014. There are some significant players entering free agency – mainly defensive end Michael Bennett, wide receivers Golden Tate and Doug Baldwin — but Seattle will likely keep Bennett and will presumably resign at least one of those receivers. Cornerback may be an issue of need, as Brandon Browner is probably done in Seattle and Walter Thurmond (among others) is a free agent and also one strike away from a year long suspension. Of course, finding diamonds in the rough at cornerback is what Carroll and Schneider do for breakfast.

The core of the team will be back next season, even if players like Sherman (this year),  Wilson (next year) and Earl Thomas will be getting massive raises soon. The Seahawks will be the Super Bowl favorite in every book in Vegas for 2014, and for good reason. There’s no reason to think they won’t be very competitive in 2015, too.

That doesn’t mean it will be a quiet offseason for either team. The Seahawks and Broncos are both already up against the 2014 cap, although each team has some easy ways to improve their cap shape. For Seattle, Chris Clemons, Zach Miller, and Sidney Rice will likely be released, but that’s hardly cause for alarm. In Denver, Champ Bailey is a likely cap cut (or restructure), and Jacob Tamme and Joel Dreessen can be released to save money and cause minimal damage.

But the future in Denver is much cloudier than it is in Seattle, and not just because of how Super Bowl XLVIII unfolded. The Denver defense was hardly a consistent source of success, but Wesley Woodyard, Robert Ayers, Mike Adams, Quentin Jammer, Dominique Rodgers-Cromartie, and Shaun Phillips  are all free agents. Getting back Von Miller and Rahim Moore will help, but the Broncos simply don’t have much talent on that side of the ball. Cornerback Chris Harris is also restricted free agent, and the Broncos must keep him and hope he recovers from ACL surgery. Remember, Darrelle Revis struggled early in 2013 after his knee surgery, and Revis was a much better player who had his injury three months earlier in the season. As a result, cornerback is a huge need for the Broncos in the offseason, even if Bailey returns (if he does, it could even be at safety).

Absent a stellar draft, the only way the Broncos will be Super Bowl contenders in 2014 is if Manning makes the team one. Of course, Manning’s been doing that for over a decade now with many changing parts. Knowshon Moreno and Eric Decker each scored double digit touchdowns and are free agents, but it’s a testament to Manning that the Broncos can lose both players and nobody will expect the offense to miss a beat. Montee Ball and either Ronnie Hillman or C.J. Anderson can handle the load at running back, and the Broncos will either add another wide receiver or simply promote Andre Caldwell. And while losing a couple of skill position players may hurt, the team played nearly the entire season without left tackle Ryan Clady, and his return should help an offensive line that was shaky down the stretch.

The biggest reason Denver will remain a Super Bowl contender is because of a weak AFC — nobody is ready to bank on the Patriots, Bengals, Colts, Chargers, or Chiefs making the Super Bowl, are they? Of course, things can change very quickly in the NFL, and it’s fair to wonder if the Broncos window is nearly closed. A schedule that features the NFC West, Cincinnati, and Indianapolis won’t be easy, which means the margin for error for home field advantage will be very thin. John Fox will return, of course, and like Seattle, the Broncos benefited from making it to New Jersey. Both offensive coordinator: Adam Gase and defensive coordinator Jack Del Rio are expected to return.

Perhaps the biggest question mark is if Manning, at 38, can do it all again.  For the second year in a row, the team had home field, and this year, the weather cooperated. How likely is the team to avoid a cold/windy playoff game next year? Can the return of Miller and Clady be enough to offset all the personnel losses? How far will Manning fall back to earth – after his 2004 season, he again led the NFL in ANY/A but dropped from 9.78 to 8.03, and saw his touchdown total fall from 49 to 28. Some regression is guaranteed, of course, but significant regression and a bad defense could lead to a 10-6 season and an early playoff exit for the Broncos.

Manning and Tom Brady were the two oldest starting quarterbacks in the league this season, and it’s fair to wonder if the Manning/Brady era is over. Manning, Brady, and Ben Roethlisberger have started 11 of the last 13 Super Bowls for the AFC. With Manning and Brady near retirement, and the Steelers organizational struggles of late, the AFC appears more wide open than it has in a very long time.