Tuesday, May 22, 2018

NFL analytics

Can Delaying the Snap Like Peyton Manning Win You the Game?

I was nerdily inspired by Marcus Mosher's Tweet about the amount of time left on the play clock when teams snapped the ball in 2017. You can see that the Super Bowl champion Philadelphia Eagles took the longest to snap the ball. But the Super Bowl runner-up New England Patriots were 29th.

So is there anything to it? Does 'Time on Play Clock at Snap' mean anything about a team's performance? Peyton Manning presumably thinks so:
An NFL Films clip, narrated by the late Steve Sabol, about how long Manning took at the line. 
It's posted to YouTube under "Just Snap the Damn Ball Colts"

To answer this question, I ran a correlation on Time at Snap vs. Winning Percentage in the 2017 season.



The time data isn't precise, because I don't have access to the exact numbers that Mosher used. I based these numbers on a visual interpretation of the graph; it's the best I can do, unless Mr. Mosher decides to send me the data file he used! Until that happens, here's the file with the numbers that I used (downloadable, .xls format).

But my analysis, such as it is, reveals an r of -0.32. This is a noteworthy negative correlation, even if the exact value of the correlation is in doubt. The true correlation might be a bit stronger, like -0.35, or a bit weaker, like -0.29. But I'm very confident that the true correlation is negative, and I'm less confident (but still fairly confident) that the actual correlation value is roughly -0.30.

The scatterplot for this result is displayed below:


It shows that, in general, the quicker you snap the ball, the lower your win percentage. New England appears to be an outlier; the worst teams generally snapped the ball most quickly.

Of course, the question is: WHY? Should your favorite team simply wait until the play clock reads :01 before snapping the ball on every offensive play?

Of course not; that would be ridiculous! I suspect that Time at Snap is a proxy for the QB's ability to read the defense and call adjustments. Granted, Brady reads defenses (and adjusts) quite well, so it's obviously not a perfect proxy! But in the NFL Films clip above, Manning's behavior supports my explanation. Good luck doing all that and then snapping the ball with 20 seconds left on the play clock!

That explanation is certainly better than telling your QB, "just wait until the play clock reads :01 before snapping the ball. If we do that consistently, we'll go 16-0 and win the Super Bowl! Because DATA!!!"

Correlation is not causation, people!...

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