Analyzing Alex Smith: Air Yards, Completion Percentage, And Depth Of Targets


I honestly wasn’t planning to write another Alex Smith post before we see actual football played on a field this year. I wrote about my initial thoughts on the Alex Smith trade in THIS POST, then I looked at how much KC fans should expect Alex Smith to improve their team in THIS POST, and then a few weeks back I examined the similarities between Smith and Drew Brees in THIS POST. I thought I was done, I mean a trilogy of posts sounds about right. It worked for The Lord Of The Rings and the Godfather movies, right? (not that my posts are in their league) Sticking with the movie parallel, it seems like three is the acceptable maximum for credibility. Once you get to Rambo 4 or the fourth Die Hard movie it starts to lose some luster. I couldn’t possibly have more to expound on Alex Smith this offseason. I should find something else to write about.


So why the change of heart?

I blame Twitter.

The list of people I follow on Twitter is made up of largely football related journalists. Is this in part because I want to hear about any spec of Chiefs news out there on the internet? Yes, however I have also found some very insightful people that have expanded my knowledge and understanding of the game. One of my favorite follows is Joe Bussell who tweets under the moniker @NFLosophy. In terms of just interesting football talk and insight, he’s a must follow. This past week he tweeted out some thoughts on some advanced statistical metrics that he feels help evaluate quarterbacks. These included “Air Yards” and “Average Depth Of Target”. Basically, these stats try to take a closer look at how well a quarterback really throws the ball.

“Air Yards” are the number of a quarterback’s passing yards that came from the ball being in the air. In other words, it breaks a QB’s passing yards into Air Yards and Yards After Catch. This allows you to see how much of a QB’s production was his throw as opposed to the yards his WR picked up. So if Matt Cassel threw a screen pass to Jamaal Charles for an 80 yard TD, Cassel would get 0 Air Yards because Charles ran all 80 with the ball in his hands. If Aaron Rodgers threw a 40 yard TD pass to Greg Jennings that he caught in the end zone, then Rodgers would get credit for all 40 yards as Air Yards. Hopefully you get the idea.

Bussell tweeted out a link to THIS SIGHT called Sporting Charts where you could see the Air Yards for all the quarterbacks for the 2012 season (and every season going back to 1990). I spent some time looking over this chart to try and see if I could understand if there was a direct relation between Air Yards and good quarterback play. The first thing I noticed on the sortable charts on that sight is that the percentage of air yards to yards after catch seems to have more to do with the ability of the receiving core than the QB. Case in point, Mark Sanchez had the highest % of air yards in the NFL last year and he’s terrible. Eli Manning was #2 behind him and he’s pretty good. On the opposite end of the spectrum Christian Ponder had the lowest % of air yards and he’s not very good, but Aaron Rodgers had the 7th lowest % in the NFL and he’s amazing. So I think we can throw out % of air yards for trying to determine how well a QB throws the ball.

The other stat on this chart that I looked at was Air Yards Per Attempt. This time a preference became clear. Look at the top ten QBs in air yards per attempt last season:

Colin Kaepernick
Eli Manning
Russell Wilson
Peyton Manning
Tony Romo
Drew Brees
Alex Smith
Andrew Luck
Robert Griffin III
Cam Newton

Now compare those to the bottom 10 QBs in air yards per attempt last season:

Matt Cassel
Blaine Gabbert
Philip Rivers
Brady Quinn
Ryan Fitzpatrick
Nick Foles
Brandon Weeden
John Skelton
Ryan Lindley
Christian Ponder

You can see that having a higher average of air yards per attempt is definitely a better indicator of good QB play, and Alex Smith is in the right group. However, I started to wonder how it was possible for “Big Arm” QBs like Jay Cutler and Joe Flacco to be behind Alex Smith in air yards per attempt. Could Alex Smith have been throwing lots of downfield bombs that we all just missed while Flacco and Cutler more often dumped off to shorter routes? The answer, of course, is no. The reason for this differential comes from their completion percentage. Alex Smith’s completion percentage last year was the best in the NFL and when you complete more passes your averages per attempt will rise.

Think of it this way. If QB “A” completes 7 out of 10 passes for 10 yards a piece (let’s pretend they are all air yards) he’ll average 7 air yards per attempt. If QB “B” completes 3 out of 10 passes for 20 yards a piece (again, all air yards) he’ll average 6 air yards per attempt. So QB “A” with his shorter and safer passes averaged more air yards per attempt than QB “B” that threw longer passes but completed less of them. So the air yards per attempt stat doesn’t really give you a good representation of the average length of a QBs thrown pass. That’s why I decided to figure the average air yards per completion instead. I didn’t take the time to figure each QBs, but here are a few that I checked to get some comparisons.

Colin Kaepernick 8.07
Drew Brees 6.89
Peyton Manning 6.66
Tom Brady 6.22
Alex Smith 6.06
Matt Cassel 5.86
Aaron Rodgers 5.82
Brady Quinn 5.50
Christian Ponder 4.07

I included Rodgers, Manning, Brady, and Brees because they are the current benchmark for great QB play. I included Cassel and Quinn so KC fans could compare Smith to what they saw on the field last season. I included Kaepernick both to show what Smith was up against in SF last year and because he had the highest average of those I looked up. Poor Christian Ponder makes my list to show you what a true check down machine looks like.

The first thing I thought when looking at that list was “Whoa, I must have done the math wrong because there is no way the average Matt Cassel completion was in the air longer than the average Aaron Rodgers completion!” These numbers are, in fact, correct. It just goes to show that Cassel’s trouble wasn’t as much where on the field he threw the ball, but how accurately he threw it there. It was also a down year for Rodgers who averaged 7.23 air yards per completion the year before when the Packers went 15-1. This wide variance got me thinking that I might want to check a larger sample size.

Over the past three years Aaron Rodgers has averaged 6.52 air yards per completion with a 67.1% completion percentage.

Over the past three years Drew Brees has averaged 6.28 air yards per completion with a 67.4% completion percentage.

During his four years in KC Matt Cassel averaged 5.98 air yards per completion with a 57.4% completion percentage.

Prior to Jim Harbaugh arriving, Alex Smith was averaging 5.45 air yards per completion with a 57.1% completion percentage.

Under Harbaugh Smith averaged 6.12 air yards per completion with a 64.3% completion percentage.

In my opinion, this clearly illustrates that accuracy is the clear indicator of long term QB success. The average Matt Cassel completion is only in the air for 0.3 yards less than the average Drew Brees completion. The real difference is that Brees completes 10% more of his passes. Since Brees completes such a high percentage, the Saints trust him with the ball and he throws the ball about 650 times per season.

Prior to Jim Harbaugh coming to SF, Alex Smith was in the “Matt Cassel Zone” of completion percentage. However, these past two seasons under Harbaugh brought Smith up into the upper tier. If Andy Reid can keep him there, the Chiefs should be in good shape.

I know some of you are probably burnt out on numbers at this point, but for you stat heads who find this kind of stuff interesting I have one more study to look at.

While researching the other statistic that @NFLosophy mentioned on Twitter, Average Depth Of Target, I ran across this GREAT READ by Mike Clay at Pro Football Focus. If you are at all interested in this type of statistical analysis GO READ THIS ARTICLE. Instead of me trying to explain what he did, I’ll let him do it.

"Today, I ran a test that weighted each quarterback’s completion percentage based on the depth of his throws. First, I examined five years of NFL-wide completion percentage data on throws made from each possible depth. This gave me an “expected” completion rate for each depth, which I was able to compare to the “actual” for each player. My sample was 83,631 aimed throws.Before I dive into the numbers, let me explain the adjusted completion percentage used for this experiment.Adjusted Completion Percentage = (Completions + Drops) / (Pass Attempts – Spikes – Throwaways – Batted Balls – Balls disrupted by a QB hit)Because we’re trying to come up with the most accurate representation of a quarterback’s ability to complete a pass, I don’t want my numbers distorted by drops and “non-aimed throws.”This article will include 10 charts. We’ll look at the best and worst Actual vs. Expected marks in five categories: All Throws, Behind the Line of Scrimmage, 0-to-9 yards, 10-to-19 yards, and 20+ yard throws."

If that last quote made your eyes go cross-eyed after all the numbers I’ve already thrown at you, I’ll try to simplify. After watching and charting every throw in the NFL for five years he figured out the average completion percentage for every area you could throw the ball to. He then looked at every QB in 2012 and looked at if they were above or below that expected completion percentage for different distance throws. To get the true accuracy of a QBs ball placement he didn’t factor drops as incompletions and didn’t factor spikes, throw aways, etc. either.

Here’s the bottom line on this study. There were only three QBs in the NFL that finished in the top 10 in terms of completing above the expected percentage rate for all four of the charted passing depths (behind the line of scrimmage, 0-9 yards, 10-19 yards, and 20+ yards). Those three QBs were Aaron Rodgers, Russell Wilson, and Alex Smith.

“Yeah, but Lyle, Smith’s passes were all a bunch of safe check downs and Rodgers throws the ball all over the field!”

If that was your response then I remind you of the air yards per completion stat that I discussed earlier. Last season the average Alex Smith completion was in the air for 6.06 yards and for Rodgers that number was 5.82. So that argument doesn’t fly.

Here’s the exact break down of the attempts, percentage of total attempts, and their adjusted completion percentage for Smith and Rodgers in each of the passing zones:

Total Numbers
Alex Smith – 203 attempts, 81% adjusted completion percentage
Aaron Rodgers – 585 attempts, 80% adjusted completion percentage

Behind The Line Of Scrimmage
Alex Smith – 22 attempts (10.8% of his total passes), 95% completed
Aaron Rodgers – 85 attempts (14.5% of his total passes), 95% completed

0-9 Yards
Alex Smith – 120 attempts (59.1%), 88%
Aaron Rodgers – 303 attempts (51.8%), 87%

10-19 Yards
Alex Smith – 42 attempts (20.7%), 69%
Aaron Rodgers – 125 attempts (21.4%), 69%

20+ Yards
Alex Smith – 19 attempts (9.4%), 47%
Aaron Rodgers – 72 attempts (12.3%), 53%

So Rodgers threw a higher percentage of screens, Smith threw a higher percentage in the 0-9 range, they were about the same in the 10-19 range, and Rodgers was higher in the 20+ yard range. In terms of completion percentage they were almost identical in every area except the 20+ range where Rodgers had a 6% advantage. Still, Smith did finish in the top ten in the NFL in that range.

“But Lyle, Smith’s sample size was much smaller. He probably just racked up some good numbers against horrible defenses in his 8 starts.”

I wondered if that might be the case too. So I looked it up. Here are the 8 teams that Smith faced last year with their ranking in passing yards allowed, passing yards per attempt allowed, and completion percentage against.

The main thing to note here is that the average pass defense rankings of the opponents he faced in his 8 games were all around 12. With 32 teams in the NFL an average ranking would be right in the middle, around 16. This means that Smith faced above average pass defenses in his 8 starts last season. I found it especially encouraging that 5 of the 8 teams he faced were in the top ten for completion percentage allowed (including 4 of the top 5). Despite that, Smith had the highest completion percentage in the NFL.

Since we determined that accuracy seems to be a better indicator of long term success, Smith’s accuracy should serve him and the Chiefs well. The fact that his top zone for targets is in the 0-9 range isn’t necessarily a bad thing. To quote from Mr. Clay in his PFF article (seriously, if you haven’t read it yet, JUST DO IT) about the top ten passers in the 0-9 yard range:

"Hey kid, want to be an NFL quarterback? Take note of this chart. It’s the only one in the article that includes Aaron Rodgers, Peyton Manning, Tom Brady, and Drew Brees, arguably the four best quarterbacks in the league."

Is Alex Smith just as good of QB as Aaron Rodgers? No.

Did Alex Smith have the advantage of having an elite offensive line, run game, and defense that took the pressure off him in San Francisco? Yes.

When Jim Harbaugh came to the 49ers he helped raise Alex Smith from the level of Matt Cassel to where you can put his numbers by the best QBs and they hold up. Does he need to prove he can still do that with Andy Reid as his coach? Yes.

The point of this post was to show that the actual passes that Alex Smith has thrown and the percentage of completions he has had these past two seasons have a lot more in common with the elite QBs in the league than the Matt Cassels and Christian Ponders of the world. Jim Harbaugh didn’t throw those passes. Alex Smith did. He has shown he has the physical tools, and more importantly, the accuracy to excel. If Andy Reid can get the same statistical averages that he had under Jim Harbaugh but with the increased attempts typical of a Reid offense, Smith could be headed for a major break out. There’s no way to know if Reid and Smith will pull it off until the regular season rolls around.

However, the next time someone is trashing Alex Smith and tells you that he has a “noodle arm”, only checks down, and always plays it safe you can tell them “Actually, last season the average Alex Smith completion was in the air longer than the average Aaron Rodgers completion and Smith was in the top ten for completion percentage for passes thrown 20 yards or further.” That should shut them up for a little while.

Then you just have to hope that Smith backs you up with his play on the field once the games count.

As always, thanks for reading and GO CHIEFS!!!!!!!!!!!!!