“The Dallas Cowboys are bound for regression.”
How many times have we heard that this offseason? Seems like just about everyday someone else is claiming the Cowboys will fall off the top of the NFC East because of “regression.” Often, the people claiming this don't even understand what regression to the mean really is.
But, alas, they still make their claims.
The thing is, the Cowboys should be expected to regress a bit in 2017, but that regression shouldn't be anywhere near enough to kick them out of the playoffs. 13 wins is an outlier season for just about any team, especially when you win as many close games (within seven points) as Dallas did in 2016.
Still, their 2016 point differential and one important equation suggest the Cowboys should still hit double digit wins this season. Let's take a deeper look.
The Pythagorean Expectation Equation
Developed by Bill James in an effort to estimate how many baseball games a team “should” win based on their run differential, the Pythagorean expectation equation has been adjusted many times over the years.
It is has been famously adjusted to estimate win percentages in the NFL, and has had quite a bit of accuracy doing so. Football Outsiders claims that between 1988 and 2004, 11 of the 16 Super Bowl winners also led the league in Pythagorean wins. They also claim that this equation is a valid predictor of improvement or regression during the following season. For example, when a team wins at least one full game more than the equation would project, they tend to regress the next year and vice-versa.
The equation itself is very simple to run, and can be seen right above this sentence. You simply take a team's points for and points against during the given year and plug them into the formula. The output is a team's estimated number of wins during that particular season.
What does this mean for the Cowboys?
Well, in 2016 Dallas scored 421 points and allowed 306. When you plug those numbers into the formula, they are estimated to win 10.88 games. Even if we round that to 11, their real win total of 13 would suggest regression in 2017. Dallas “overachieved” by these standards, and would be expected to fall back towards the original expectation.
While regression is predicted through this equation, it should not be enough to knock them out of the postseason. Dallas was fourth in the league in point differential a year ago, and would still be predicted to be around 10-6 if this model (and Dallas' numbers) hold constant.
What's most interesting, however, is what this model expects from the Philadelphia Eagles this season. According to the formula, Philly underachieved with just 7 wins in 2016, and should be able to eclipse .500 this year. By their point differential, the Eagles should have won about 9 games a year ago.
If these models hold true, the NFC East race could get very interesting this season. But, Dallas' top challenger may not be the team who everyone expects it will be.