The past 18 months or so have given rise to some surprising events, both on the world stage and, most interestingly for our purposes, on the football stage.
Tom Brady left the team he won six Super Bowls with, only to win another with Tampa Bay, a team that hadn’t so much as come out on top in a playoff game since its last triumph in 2002. The Patriots, following their first losing season since Drew Bledsoe was their full-time starter in 2000, didn’t just dip their toes into the free agency market; they splurged. New England signed tight ends Jonnu Smith and Hunter Henry to market-level deals and gave edge defender Matthew Judon one of the richer contracts in his position group. After it was all said and done, the Patriots acquired 10 free agents, improving the most of any team, according to PFF's improvement index.
This got me thinking about the culture in New England … the so-called “Patriot Way.” Anecdotally, we’ve seen the story play out a bunch: A player plays well for New England, Bill Belichick unloads him and he doesn’t play so well for his subsequent team. Is that dynamic consistent with the data?
Furthermore, the other side of the coin is going to be on trial this season. While we’ve seen players like Stephon Gilmore and Randy Moss take off when joining the Patriots after stints with other teams, there have been a number of cases where that has not been the eventual outcome (Albert Haynesworth, Joey Galloway and Chad Johnson, to name a few).
In this article, we’re going to use PFF’s wins above replacement metric to explore how players do in and outside of the Patriots’ system. PFF WAR has the advantage of being a metric that is part efficiency and part volume, which helps with sample size issues in the case where someone goes to another team and barely plays. PFF's Timo Riske recently wrote about how this metric could be used in age curve analysis, which we will touch on at the end.
The Simplest Analysis
The simplest analysis is to look at how players who played in both New England and somewhere else have fared in terms of WAR on a per-season basis. As expected, players who have played in New England and with another team are almost twice as valuable for the Patriots than for anyone else (WAR = 0.141 per season with the Patriots versus 0.085 with another team):