Matt’s Musings | NFL Data Study, Week 13

Every Monday, I find myself in a bit of NFL data purgatory. We’re waiting for the week to come to a proper ending, and the data is still yet to be finalized. It’s a great time, however, to look at some historical trends and do some digging on some things we can leverage in the upcoming week.

This piece will be out Tuesdays but won’t have the same format or topic each week. The formula will change as I poke around with the data we have access to here. It’ll just be my musings on something that caught my eye. If there’s something to it, I’ll give you some way to leverage the conclusions in fantasy for the upcoming week.

What did that announcer just say?

I wanted this piece to challenge conventional wisdom and one of these “football guy” sayings came out during the Giants broadcast Sunday. It was something along the lines of, “You can’t underestimate the value of a 1-yard run and how it wears down a defense.” It was first and 10. Now, on the one hand, I get it — there’s a physical element to football that I (and my spreadsheets) might never be able to comprehend. But as a community, we are absolutely, unequivocally positive that a 1-yard run on first and 10 does nothing to help your team. 

“But Matt, don’t you see that spike in the positive section of the graph?” Yes, yes I do. But we’re looking at just over 8% of runs here with a positive EPA and it’s very situation specific. In fact, on average, a first and 10 has an expected point value of about 2.7 EP while a second and 9 drops to 1.8 EP. 

With each subsequent down that passes, expected points go down when you’re not gaining yards. That’s not a life-altering realization, obviously, but it’s an important step in our process here. Side note: The first down line is a bit squirrelly because of some small samples of random yards to go after penalties.

You’re probably thinking that I spent way too much time cleaning data, making a graph, and writing about a stupid quote by an announcer just to show that expected points on a first and 10 are higher than on a second and 9. You’d be absolutely correct, but it’s a jumping-off point for some of the analysis I’ve been doing, so don’t bail on me just yet. 

Do defenses ‘wear down’ from first-half runs?

There’s a lot to unpack there. The simplest way to look at this, though, is by comparing the relationship between first-half runs and how efficient runners are in the second half. 

Do you see that nice, basically flat line? That’s our trend line. The trend line shows the relationship between the two variables on the plot. These two variables, number of first-half runs and second-half yards per carry, have no relationship with each other. Less than 2% of a team’s rushing efficiency in the second half can be explained by the number of rushes a team had in the first half. Maybe that isn’t fair, though. Games still remain pretty close in the third quarter often. Let’s see what happens when we compare the number of rushes from the first three quarters to fourth-quarter/OT rush efficiency. 

Hmmm… So even 45 minutes of a rush-heavy attack doesn’t equate to higher efficiency. That could easily be explained by garbage time, right? Teams that are trying to milk the clock aren’t going to break off big runs, they’ll go down once they get the first down or sacrifice yards for ball security, right?

Nope. Still nothing there. Maybe there’s not a magic number of these early rushes that makes it happen, but the effects just happen slowly as the game goes on. 

Wrong again. The fact of the matter is that this idea of teams “wearing down” opposing defenses with these rushes doesn’t jibe with reality. It’s a common trope across football to say that these effects exist. It just doesn’t jibe with intuition, though, because if the defense is getting physically punished on all of these plays, then the offense is also exerting energy throughout the game, as well. 

Is it really that big of a deal when teams are hell bent on running?

Looking through the data, teams have a higher chance (73.5%) of getting another first down on a given series when they pass on first down compared to when they run on first down (70.8%). That’s not a huge gap on a per play basis, but small edges compound over time to add up over the course of a game or season. 

In a given game, most teams will have somewhere between 8 and 12 offensive drives. If you’re giving up 3% of your chance at a successful series every time you run, you could be sacrificing 5-10 drives for the season. Given an average team in points per drive, that could be about 20 fewer points across the season. It doesn’t sound like a lot but these small edges and leaks compound over the course of the season. 

First-down pass rate in these neutral situations explains about 23% of scoring. As you can see, there’s a fair number of outliers. The bottom-right quadrant here is a quartet of teams that are actually making the right decisions on first down and still have nothing to show for it. Of the 13 teams in the top-right quadrant, which is where you are seeing good decisions and the results to show for them, nine would be in the playoffs if they started today. 

Key Takeaways

• The Jets/Giants/Jags are just incredibly awful in this metric. They’re leaving 5+ points on the board each game. 
• The entire AFC West is bunched up -2 to +1 points over expectation.
• The Cowboys and Buccaneers are hovering around +7, which means they’re scoring an extra touchdown on average.