If you’re looking for a good singular statistic to correlate with success (besides W/L record), it’s hard to go wrong with turnover differential. This measures the difference between takeaways and giveaways to provide a very simple output of: “Did you take or give the ball away more?”
It’s not a perfect measurement. The Philadelphia Eagles have made the playoffs the last two years with a negative differential for instance. But in general it’s an easy sell to say you wanna be on the good side of this metric. How have the Sean McDermott-led Buffalo Bills done?
As far as analytics-based discussions go, this is extraordinarily straightforward. Here’s a chart that breaks down how often the Bills took the ball away vs. how often they gave it away in the three years that Sean McDermott has been the head coach.
It’s no surprise the two playoff years had positive turnover differentials to go along with their higher win totals. Of note is that the Bills have been remarkably stable when it comes to takeaways. The 2018 season is the anomaly, or closest thing to one anyway. League averages have remained remarkably stable at 22.1 turnovers per team in 2017, 21.8 in 2018 and 22.2 this year. The Bills then have tended to hover around average.
This means the variance in turnover differential for Buffalo belongs to the offense. This year’s offense was tied for 11th-best in avoiding a turnover with 19 giveaways. It’s still average (according to the Rule of Four), but on the better side of the fence. They were sixth best in 2017. The 2018 season was one slot from the bottom.
Turnover problems are a quarterback problem
A quick glance at this should be all the proof we need. Of the two types of turnovers, interceptions are almost exclusively a quarterback stat. Looking at fumbles lost then, the top 11 players are quarterbacks. It’s not until we get to number 12 on the list that we see a running back. Chris Carson of the Seattle Seahawks has that notoriety with four lost. He also shares the 12 spot with a quarterback.
If you needed more proof, here’s the breakdown of quarterback responsibility for the last three years.
Feel free to dive in as deep as you like with this chart, I’ll just skim the surface. In 2019, quarterbacks accounted for all but one turnover. Yes Devin Singletary was scary a few times and you could argue we were lucky, but it’s a very lopsided contest.
Josh Allen could stand to cut down on the fumbles. It’s actually encouraging, though, that his overall turnovers remained stable at 14. A major increase in playing time means his turnover rate dropped.
One last thing; 2017 and 2018 are really good at illustrating how a bad quarterback can get you behind in a hurry. Derek Anderson and Nathan Peterman both had limited time on the field, but created a lot of turnovers.
What will 2020 hold? There’s a chance the defense will “regress” some. They’ve been a bit over the average so falling a little below is reasonable. It’s also reasonable they maintain their current numbers, which is my guess. On the offensive side of the ball, I don’t think Allen’s improvement in this area is a mirage. He cut down on turnovers during the slate of games where he faced the best defenses. That should result in another year on the positive side of the ledger, which should bode well for team success.