In early September, Adam Steele, a longtime reader and commenter known by the username “Red” introduced us to his concept of Marginal Yards after the Catch. Today is Part II to that post. Adam lives in Superior, Colorado and enjoys digging beneath quarterback narratives to discover the truth; hey, who can blame him?

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Introducing Marginal Air Yards

There are three components of Y/A: Completion %, Air Yards/Completion, and YAC/Completion. In my last post I looked at YAC, so today, let’s look at the other two components. By multiplying completion percentage and air yards per completion, we get air yards per attempt, which we can then modify to create Marginal Air Yards (mAir):

mAir = (Air Yards/Attempt – LgAvg Air Yards/Attempt)*Attempts

Here are the yearly Air Yard rates since 1992, with the table sorted by Air Yards per Attempt::

Air Yards/Attempt have remained fairly constant over the years, despite the substantial increase in overall passing efficiency in recent seasons. The boosted efficiency of today’s passing game is almost entirely a result of increases in YAC and decreases in INT %; completion % has also steadily risen over the years, but it’s balanced out by a large decrease in Air Yards/Completion. In fact, the average depth of completions has fallen more than a full yard (7.16 to 6.04) since 1992. However, it’s interesting to note that 2004 saw a major spike in Air Yards/Completion, which just happens to be the last time illegal contact penalties were re-emphasized (we’ll have to revisit this topic once the 2014 season is in the books).

Now, let’s look at the top 50 seasons of Marginal Air Yards since 1992.

This list represents nearly all of the greatest QB seasons of the last two decades, and not a single season that would be considered below average. It makes sense that quarterbacks would have more control over Air Yards than YAC, because Air Yards are created with the ball in the QB’s hands, while YAC happens in the receiver’s hands. However, there seems to be one glaring exception to that rule, and his name is Randy Moss. Four of the top 20 mAir seasons have occurred with Moss as the #1 receiver, and represent by far the best mAir seasons for each of his quarterbacks (Culpepper, Brady, Cunningham, and George). This doesn’t move Moss ahead of Jerry Rice for the GOAT title, but in my opinion it builds on Neil’s work and definitely moves him closer.

Setting aside the Randy Effect, Peyton Manning is the undisputed King of Air Yards during this era. He’s registered six seasons in the top 50, while nobody else has more than three. Somewhat surprisingly, Mark Brunell makes three appearances here. We forget about him because he played in Jacksonville and never reached the Super Bowl, but the Coughlin-era Jaguars had a potent passing attack, and Brunell was doing the lion’s share of the work with his excellent downfield throws. If you ignore RINGZ theory, Brunell ran Coughlin’s offense much better than Eli Manning ever has. The most prolific aerial attack of the last two decades is not immediately obvious, because it was spilt between Kurt Warner and Trent Green. The 2000 Rams totaled exactly +1000 Marginal Air Yards, which essentially laps the field (there are only eight other seasons above 600 mAir). Remember, that team went 10-6 despite finishing dead last in scoring defense. Greatest Show on Turf indeed.

What about the worst QB’s at producing Air Yards? Here are the bottom 50:

A quick perusal of this list reveals the validity of Marginal Air Yards in measuring a quarterback’s contribution (or lack thereof) to his passing offense. The worst mAir seasons are basically a who’s who of impotent quarterbacking, with names like Harrington, Campbell, Fitzpatrick, and Boller making multiple appearances. However, there are a few shockers, most notably Brett Favre showing up three times. Despite his reputation as a wild gunslinger, he was actually a Captain Checkdown for a good portion of his career. Favre’s total career mAir is a dizzying -1335, ahead of only David Carr and Joey Harrington. I did NOT see that coming. The other QB who underthrows his reputation is Donovan McNabb, posting two seasons in the bottom 50 and a career total of -1223. I had always thought of McNabb as a guy who completed plenty of deep passes to counterbalance his low completion %, but apparently that was not the case. He really padded his stats with all those screen passes to Brian Westbrook, and it makes his historically low INT % look less impressive (although low Air Yards didn’t help Favre avoid INT’s).

Do Air Yards affect YAC?

Before I started crunching numbers, I expected there to be a significant inverse relationship between Air Yards and YAC, where short passers would produce the most YAC and deep passers the fewest. It turns out the effect is real, but fairly muted. At the season level, there was a -0.26 correlation between Air/C and YAC/C, with an r^2 of just 0.07. In other words, only 7% of the variance in YAC can be explained by the variance in Air Yards. To test this further, I checked the consistency of mAir and mYAC. Starting in 2007, I measured the year-to-year correlations for both metrics, including all QB’s who threw at least 100 passes in year n and year n+1. Here are the correlations:

It appears that Air Yards are roughly three times as sticky as YAC from season to season. From this, we can infer that Air Yards are primarily the domain of the QB, while YAC is mostly a product of coaching, receiver skill, the defense’s ability to tackle, and a heavy dose of plain old luck. The oft-proposed theory that a QB can increase his receivers’ YAC by hitting him perfectly in stride appears to be minimal. However, I’m willing to believe that there are rare exceptions, such as Joe Montana and Steve Young, whose Y/A often greatly exceeded that of other QB’s despite playing in short passing offenses. My data set includes most of Young’s 49ers career (1992-1998), and he was well above average in both mAir and mYAC (+1221 and +1620, respectively).

Coming soon: In my final post in this series, I will be tying together mAir and mYAC, looking at the career totals for every QB since 1992.

References:

Sporting Charts (Air Yards data)

Pro Football Reference (standard passing stats)