You like that? Evaluating Kirk Cousins' 2015-2016 performance

After 4 long years, it seems that the Redskins may have finally found some stability at quarterback after mortgaging their future for the injury prone Robert Griffin III.  Interestingly, the rise of Cousins and Fall of Griffin might have been predicted by the 26-27-60 rule, though like any predictive rule, it has its limitations.

At first glance, Cousins had a good year, averaging a passable rating of 100.2 over the course of the 15 meaningful games that he started this season.  With a win over the Philadelphia Eagles in Week 16 locking down 1st in the NFC East, Cousins has earned some richly deserved rest in Week 17 which is the justification for leaving week 17 out of the calculations.  

However, with a standard deviation of 31 points in his passer rating, it appears that Cousins may have some room to improve in terms of consistency.  As a picture is worth 1000 words, we'll examine a time series plot of his passer rating by date:

It's pretty clear from the plot that there is a significant improvement in Cousin's passer rating over the course of the year (r=0.55, 95% CI: 0.05-0.83, p =0.034), though there appears to be a marked difference between his home and away performances (means ± SD of 115.4±30.1 vs. 83.1±22.6, p = 0.035).  This difference isn't alarming, as this trend is quite common in recent franchise QBs:

Peyton Manning: 101.6±26.9 vs. 94.9±26.6, p = 0.045
Aaron Rodgers:  107.3±23.4 vs. 99.0±26.1, p = 0.013
Drew Brees:  99.7±26.4 vs. 93.4±27.2, p = 0.084

Still, the late season improvement is comforting to the Redskins fan, particularly as it manifested itself in the W/L column at a time when the Redskins need to decide how much to shell out to retain Cousins for the 2016-2017 season.  However, the difference may be due to the fact that DeSean Jackson sat the first 7 games of the season (but that's an entirely different post).