How Important Are Air Yards to Quarterback Production?

Alex Smith takes a lot of heat for not being able to throw the ball vertically downfield. Or, at least, he takes a lot of heat for not throwing the ball down the field very frequently.

But is it warranted?

I mean, think of this intuitively. If a team gains 10 yards on a play where the ball traveled 10 yards through the air to a receiver, is it any different than a team running a 1-yard bubble screen that features 9 yards after the catch? If a short slant pattern creates 32 yards after the catch was made, is it any different than a touch pass down the sideline that goes the same distance?

From a production standpoint, no. The answer to both of those questions is no.

Passing plays aren't that simple, though. And when you take a deeper look at quarterbacks who can get some loft on the ball, it becomes pretty clear: air yards matter.

Measuring Production

If you're new to numberFire, then you're more than likely unaware of our Net Expected Points (NEP) metric. In essence, it's our way of showing what actually happens on a football field -- how a player performs versus expectation -- as opposed to just looking at traditional statistics like yards and touchdowns. Because not all plays that go for the same yardage are created equally: a 10-yard gain on 3rd-and-12 means a lot less than a 10-yard gain on 3rd-and-9.

For more on Net Expected Points, check out our glossary.

With NEP, quarterbacks can be measured in sum or on a play-by-play, efficiency basis. Because most quarterbacks create positive plays -- passing is more effective than rushing in the NFL -- a cumulative Passing Net Expected Points total is going to skew towards passers who throw the ball more often. The more passes, the higher chance a quarterback is adding positive points for his team.

When we divide a quarterback's Passing Net Expected Points total by the number of drop backs he sees, though, we get efficiency. We get Passing NEP per drop back. And that levels out the playing field.

Basically, Passing NEP per drop back tells us how many points a quarterback is adding with each drop back he takes. If he throws a pick-six, that's bad news for his rate. If he tosses a huge touchdown, then we'd expect his average to rise.

It's important to remember and know that Net Expected Points doesn't look at how these plays are accumulated. In other words, like the examples above, if a quarterback throws a 10-yard pass on 3rd-and-9 from his own 32-yard line, it'll count the same if he did it with 3 air yards, with 6 air yards, or with 10 air yards.

But the "how" is actually pretty important.

Air Yards in 2016

Air yards are just that: the number of yards a ball travels through the air. It's the number of yards thrown minus the number of yards after the catch.

Here's a quick look at the quarterbacks with the highest air yard totals from 2016:

Now, similar to total Passing NEP, this doesn't tell us a ton. It tells us something, but not a whole lot. After all, a player with a lot of air yards could've just thrown the ball of a hell of a lot, no?

What we really need to look at is air yards per attempt. Like Passing NEP per drop back, that stabilizes things a bit.

The chart above consists of quarterbacks with 100 or more attempts this year -- anything lower would've yielded some really bizarre numbers, like Derek Anderson as the top air yards per attempt leader despite barely playing football in 2016.

But you can see how this is different -- and more accurate -- than the original table. Instead of looking at all of the yards, we're looking at them on a per-attempt basis. It equalizes the sample.

So back to the original question: how do air yards impact quarterback performance?

Air Yards and Quarterback Performance

Because we've got our nifty Net Expected Points metric, the rest of this is pretty straightforward. The chart below depicts air yards per attempt versus Passing NEP per drop back averages for all 100-plus attempt quarterbacks since 2011, the year the quarterback position became broken in the NFL.

See any correlation?

You should.

What this is showing is that there's a relatively strong connection between how far a quarterback is throwing the ball per attempt and how many actual points he's producing for his team with each drop back. And keep in mind, Passing NEP per drop back includes sacks, too.

You'd think a passer getting more air under the ball would have a higher chance to be sacked given the time needed in the pocket (this isn't tested, just a hypothesis), so this just enforces the idea that air yards do, indeed, matter.

There are naturally going to be exceptions to the rule, which is why the r-value here is closer to 0.60 rather than 1. Tom Brady's a great outlier example: of the 252 quarterbacks in the sample, Brady's best air yards per attempt season ranked 64th. In fact, in 2013, his air yards per attempt was just 3.49, or the 178th-highest rate in the cohort. Meanwhile, we know Brady is a great passer who's always ranked in the top-five in Passing NEP per drop back.

Maybe this just plays into his brilliance. Maybe Tom Brady is so good because getting consistent production through yards after the catch is difficult, but he knows how to maximize that aspect of the game.

And, look, a lot of this data isn't even necessarily skill-based. A quarterback may be in an offensive system that calls for short passes. Or maybe the signal-caller just doesn't have time to throw the ball downfield with any sort of frequency.

But what we do know is that throwing the ball down the field does matter. Air yards really are important.