2021 NFL MVP: Los Angeles Rams QB Matthew Stafford closing on Chiefs’ Patrick Mahomes

Week 5 of the 2021 NFL season was illuminating for all of us. Buffalo Bills quarterback Josh Allen has apparently overtaken Patrick Mahomes as the best quarterback in the league, Lamar Jackson and Tom Brady are the new MVP favorites and Justin Herbert continues to amaze fans and analysts alike. 

Of course, some of these Week 5 takeaways are more irrational than others, so let's dive into the PFF data to sort through them.

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Before we get to the Week 6 NFL MVP rankings, here's a short overview of the methodology:

We trained a model to predict the winner of the MVP award based on only three regular-season parameters after Week 18 concludes:

1. The number of wins and how that ranks across the league
2. Rank in the division
3. Expected points added (EPA) per play and how that ranks across the league

Since the model works with regular-season stats in hindsight, we need to simulate the remaining games of the season to find results with which we can feed the model. So, we utilize PFF's weekly win total simulations and a Bayesian updating method to simulate each quarterback’s EPA per play.

During the season, we update our beliefs on all quarterbacks with Bayesian updating, incorporating up-to-date EPA per play and making adjustments based on PFF passing grade, our charting data — which can identify plays with bad results that aren't the quarterback's fault — and the quality of defense faced.

Using these updated beliefs, we can simulate the EPA per play for the remainder of the season for each quarterback.

The number of wins and whether a QB wins his division is obtained from our weekly win totals simulations.

The goal isn’t to describe who would be MVP if the season ended right now, but rather to predict who will have the best combination of individual stats and team wins at the end of the season.

Defense adjustments

First, we adjust for each defense to find which quarterbacks played the most difficult schedule (and receive the highest positive adjustments). Since it’s still early in the season, the defense adjustments are based on both opponent-adjusted performance this season as well as a prior from the offseason. With each passing week, the prior will play a smaller role and will be fully disregarded after eight weeks of play.

The defensive strengths of the teams lead to the following adjustments for quarterbacks (a positive adjustment means a difficult schedule so far; a negative adjustment means an easy schedule):

Of course, it’s also interesting to look at future strength of schedule based on the current strength of defenses. In this chart, a positive number means an easy future schedule (i.e., the player is supposed to generate more EPA due to playing easier defenses):

The Favorites

The Seahawks’ lackluster start aside, Russell Wilson is essentially no longer eligible for the award because he will miss multiple games due to injury.

Josh Allen, meanwhile, maneuvered himself into the conversation by beating the Chiefs in prime time, though we are not as high on him as the betting market is.