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Odds against Seahawks replacing Darrell Bevell leading to more scoring

NFL: Seattle Seahawks at Arizona Cardinals Mark J. Rebilas-USA TODAY Sports

Yesterday I took a quick look at what changes teams that made the playoffs in 2016 but missed in 2017 have made so far this offseason in terms of their coordinators. Now to take a look some at the data that is available regarding teams in situations similar to the Seattle Seahawks in terms of making changes to their offensive coordinator, but leaving the head coach in place, in order to start to build expectations for 2018. Obviously any expectations for the 2018 season will depend on multiple things going forward, including exactly who is hired as the new offensive coordinator, which players the team signs versus loses in free agency and of course the additions the team makes to the roster though the draft.

However, since that is all months away, and everyone is so excited about how explosive the 2018 Seattle Seahawks offense will be, I’m simply here to rain on everyone’s parade. Now, I could easily be wrong, but I simply go where the data points, so for at least the next eight months everyone can simply laugh at my absurd predictions that the offense may not improve into a juggernaut in 2018.

In any case, I went through every coaching change over the last twelve years, looking at the impact of changing the offensive coordinator when the head coach remained the same. During the twelve year period of 2006 to 2017 there were 67 instances of a team changing its offensive coordinator but not changing its head coach, and for each of those 67 instances I looked at the difference between average points scored in the season of the change compared to the prior season. What I found was that of those 67 instances, in only 29 cases did scoring decline, which seems great because that means there is somewhere in the neighborhood of a 55-60% chance of the 2018 Seahawks scoring more than the 2017 team and only a 40-45% chance of the team scoring less.

In order to not fill up the article with a giant spreadsheet of data, but to show what the distribution of scoring changes season to season for these 67 teams looks like, here is a histogram showing where each of them falls.

That definitely seems like it could be some good news, and there are obviously a lot of teams over the course of the last 12 seasons that have made the changes Seattle has made and then seen the offensive output improve. So, I sat down and started parsing through all the data in order to try to understand what changing the offensive coordinator is likely to mean for the Seahawks. The first thing I did was to look at the teams that saw the biggest increase in offensive production, so I immediately pulled up the data for the 21 teams that saw an increase of 3 points per game or more after changing the offensive coordinator.

This is when things started to get ugly. In short, of the 21 teams that saw an increase of 3 points per game or more after installing a new offensive coordinator but not changing head coaches, 20 of the 21 scored 20.0 points per game or fewer in the season before the offensive coordinator was changed. In fact, a majority of the 21 teams (12 of the 21) averaged more than a full standard deviation (roughly 4-4.2 points per game, depending on the season) below league average in points scored per game, so seeing a large increase would be expected simply from the effects of regression to the mean. The only team of the 21 that averaged more than 20 points per game in the season before changing coordinators was the 2012 Denver Broncos, who averaged 30.1 points during Peyton Manning’s first season in Denver and 37.9 in his second season of 2013. So, to summarize, the overwhelming majority of the greatest increases in scoring in the season after a team changes offensive coordinator but retains the same head coach came from teams that were horrible to below average the prior season.

Intrigued, I wanted to know what the data looked like for teams that were above average in scoring, such as the 2017 version of the Hawks. Thus, I next took a look only at teams that had finished above average in scoring in the season prior to making the change at offensive coordinator. There were 25 teams that saw a new offensive coordinator take over after having finished above average in scoring, and of those only seven increased their scoring in the subsequent season. Here is what that distribution looks like.

That histogram is not very encouraging, and it also fails to show that a majority (4 of 7) of the teams that increased their scoring increased the points they scored by fewer than 1.5 points per game. So, here is a second distribution with smaller spacing between groupings which may be a bit more telling.

Given the parameters used here, 18 of 25 (72%) of teams saw a reduction in scoring and only 3 of 25 teams - just 12% - of teams that meet these criteria increased their scoring average by more than 1.5 points per game. In my opinion, this is not great news for those hoping for a massive offensive improvement by the team in 2018. The sample size is obviously small at just 25 such teams, but with the numbers so overwhelmingly lopsided, it’s hard to make much of an argument for a large improvement. That one team way over on the right side is once again the 2013 Broncos.

Wanting to get the numbers for those teams in as close to the situation the Seahawks are in as possible, I narrowed the scope to look only at teams that were 0 to 0.5 standard deviations above league average for scoring in the season prior to changing offensive coordinators. That yielded only eight teams over the past twelve seasons, and only two of those eight teams saw an increase in points scored per game the following season. Those two were the 2007 New York Giants and the 2012 Dallas Cowboys, which saw scoring increases of 1.1 and 0.4 points per game, respectively. On the flip side, six of the eight teams saw scoring reduced, with five of the six teams seeing points scored drop by a field goal or more per game.

In summary, while the sample sizes are small, the data available indicates that the 2018 Seahawks offense is more likely to see a decrease in points scored per game than an increase. Obviously there are a lot of variables that will come into play going forward, but teams in situations similar to the Seahawks have traditionally not seen a marked increase in scoring after changing their offensive coordinator.

This obviously does not mean that the Hawks are guaranteed to see a decrease in offensive production in 2018, but like in any situation when making projections for the future, the best guide is the past. And the past indicates that it’s more likely the Seahawks score less next season than this year.