Air Yards Explained
What Are Air Yards?
It turns out that a wide receiver’s production depends on four distinct areas of play.
- First, a receiver needs to run a route at the depth specified in the play design. Route depth is typically tailored by the coaching staff to the talents of the player.
- Next, the receiver needs to earn a target. He can do this by getting separation, getting his defender’s hips turned, or simply out jumping his man.
- Third, the receiver needs to catch the ball thrown in his direction. A receiver’s ability to make catches is dependent on a number of factors, including the accuracy of his quarterback, but the most important factor—by far—is how deep down the field his route took him. Shorter passes are caught far more frequently than deep passes.
- Finally, once a catch is made, a receiver needs to create on his own in the form of Yards After the Catch (YAC). Like catch rate, yards after catch is largely dependent on the depth of the pass.
Air Yards
The common thread that weaves these parts of receiver play together is target depth—also known as air yards. Air yards can be divided into completed air yards and incomplete air yards. Completed air yards are just standard receiving yards minus YAC. Completed air yards would exactly equal a receiver’s total receiving yardage if every time he caught a pass he just fell straight to the ground, like Dez Bryant in 2017.
Incomplete air yards are exactly what they sound like: targets that were off the mark, dropped, or broken up by a defender.
When you add completed and incomplete air yards together, you get total air yards. Air yards are an almost perfect measure of quarterback and coaching intent. The coach and quarterback want the receiver to secure those yards, and as such, they are a window into their thinking and mindset. We can use air yards to help us unearth which receivers the quarterback and coaches would like to see get the ball—knowing that has predictive value.
aDOT (Average Depth of Target)
If you divide air yards by targets, you get ESPN Fantasy guru Mike Clay’s Average Depth of Target. This metric tells you how deep a receiver ran his routes and how many air yards he saw per target on average.
RACR (Receiver Air Conversion Ratio)
If you divide receiving yards by total air yards, you get a metric I developed called Receiver Air Conversion Ratio (RACR). Another way of formulating RACR is Yards Per Target divided by aDOT.
What’s nice about RACR is that it rolls up catch rate and YAC into one metric, and it answers the question: “At the depth of target a player is targeted the most, how efficient was he?”
Year-Over-Year Stability
Probably the most important thing about aDOT and RACR is that they are stable year to year, especially when we look at the career-to-date versions of the stats.
| Stat | Correlation Coefficient | r-squared |
|---|---|---|
|
Career aDOT |
0.72 |
0.52 |
|
Career RACR |
0.63 |
0.40 |
|
Career YAC Per Target |
0.54 |
0.29 |
|
Career Catch Rate |
0.44 |
0.19 |
|
Career Yards Per Target |
0.28 |
0.08 |
Career aDOT and RACR are more predictive than career YAC per target, catch rate, and yards per target. The important point is that RACR is an efficiency metric, and efficiency metrics are generally terrible predictors of future performance in football. Career RACR is almost as sticky as volume-based measures of receiver talent like air yards and targets, on a per game basis.
Using RACR and aDOT to Project a Receiver
Both aDOT and RACR can help us make better forecasts. For example, if we think a player has a solid chance of seeing 130 targets in an upcoming year, we can do things like the following to estimate his receiving yards:
130 targets * career aDOT * career RACR = projected receiving yards
Assuming our target projection is good, the receiving yards estimate from the above formula will be the most accurate we can create without resorting to fancy machine learning modeling.
Conclusion
Air yards belong to the receiver more so than the quarterback. A quarterback's job is to deliver the ball on time and on target to a receiver who has earned the target. A receiver’s job is to run his assigned routes—routes tailored specifically to his unique skill set—and earn those targets. Because the depth of the route is completely in the hands of the receiver, and the longer the throw the lower the YAC and catch rate, it makes sense that depth of target—air yards—is an incredibly powerful way to understand receiver performance.
Photo by Dylan Buell/Getty Images.
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