Luck, Penalties, and Turnovers

by Eric Eager|November 21, 2023


As the 2023 NFL Season enters Week 12, the end of the regular season is in sight. Teams like the Eagles and the Chiefs are positioning themselves to earn a bye in the playoffs, while the 49ers, Cowboys, Lions, Ravens, and Dolphins are all nipping at their heels should they falter. The season is a marathon, not a sprint, they say. 

However, the NFL season is quite… sprinty. Enough so that a team can generate results above and beyond its weight class for long stretches of the season at a time, if not the entire season. Take, for instance, the 2022 Minnesota Vikings, who finished the year with a negative point differential but a 13-4 record. Assuming they were a 50/50 team in all 17 games a year ago, a 13-4 or better record happens about two-and-a-half percent of the time, which is not actually that low as far as outcomes go. 

Despite five wins in a row, analysts say Vikings are still unluckiest team in the NFL | 

This year the Vikings have one more loss than last year’s team, at 6-5, but have been able to do so without their starting quarterback, their best wide receiver, and after making significant modifications to an aging roster in the offseason. One can argue that they are a fundamentally better team than they were a season ago, using crude estimations like point differential or more in-depth ones like DVOA and the like.  

The luck profile for the Vikings, along with every team in the NFL, is an interesting one. On one hand, only New England and Carolina have lost more Expected Points Added (EPA) to turnovers lost versus turnovers forced than the Vikings, who after Sunday night’s game are -35.4 EPA. Standard estimates for what a win is worth at the NFL level is about 35 points, so one can say that Minnesota has lost roughly a win from turnover luck in 2023. 

On the other hand, though, only the Jaguars have earned more EPA on penalty differential than the Vikings have, with Minnesota gaining 24.5 EPA back on penalties. Given the high-profile nature of officiating mistakes across the league, one could ask the question as to which one of these measures is more fundamental to the luck or lack of luck the Vikings, and other teams in the league, have gotten this year.  

Let’s dig in. 

Firstly, there is little evidence that turnover luck and penalty luck are related to each other, with a correlation of r = 0.126 within a season between turnover EPA differential and penalty EPA differential (2011 to present). There’s almost no predictive power between one or the other, either, with penalty EPA differential having a correlation of r = 0.031 with next-year’s turnover EPA differential, and r = 0.012 in the other direction. 

However, while there isn’t much of a connection between turnover and penalty luck – i.e., there really isn’t a connection between being disciplined in one area and not another – there is signal year-to-year in terms of avoiding and inducing penalties. Penalty EPA surrendered from season to season is correlated at a rate of r = 0.186, which is (predictably) higher than the year-to-year correlation in penalty EPA received (r = 0.113). However, the difference, the net EPA generated by penalties for and against, is surprisingly stable (r = 0.211).  

On the other hand, turnover EPA differential isn’t so well behaved, and the EPA surrendered (r = 0.100) and generated (r = 0.098) are noisy year-to-year, but the differential – the net EPA on turnovers, has a correlation coefficient close to zero (r = 0.043). 

Thus, from the perspective of Kevin O’Connell’s Minnesota Vikings team, they are indeed more on the unlucky side than not, as what they are excelling at – limiting their own penalties and inducing other teams into mistakes – is more fundamental than what they are struggling at – which is inducing turnovers from opponents and avoiding such turnovers on their account. In general, if you’re anxious to buy or sell teams during the season, you can be more comfortable buying into a team with a good penalty differential and selling teams with a bad turnover differential. Towards that aim, here have been the best teams in terms of penalty differential: 

Team  EPA gained on penalties  EPA lost on penalties  Net EPA on penalties 
JAX  78.1  -48.1  30.0 
MIN  82.6  -58.1  24.5 
PHI  65.2  -45.6  19.7 
TB  72.6  -55  17.6 
CIN  61.4  -49.3  12.1 

Here are the worst teams in terms of turnover differential: 

Team  EPA gained on turnovers  EPA lost on turnovers  Net EPA on turnovers 
NE  38.3  -79.4  -41.1 
CAR  40.9  -78.1  -37.1 
MIN  69.2  -104.4  -35.4 
WAS  56.6  -90.4  -34.7 
ATL  51.6  -83.5  -31.9 

Notice, despite some narratives, the defending Super Bowl champion Kansas City Chiefs are not earning favor from officiating, far from it. 

As always, keep in your mind as you traverse through this and each NFL season, as we’re constantly exploring new ways to convey the results of our analyses in the form of tools for our loyal consumers.


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