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Saturday, January 10, 2009

Smart Notes - January 10, 2009

1. Air Yards. I want to highlight one of my favorite new stats: Air yards, as developed by Advanced NFL Stats:

If football were a brand new invention, and we had to decide how to credit the various amounts of yards gained to various players, how would we do it? If I said, "There's this kind of play called a pass, in which a thrower passes the ball to a another player who then runs with it as far as he can. I say we credit all the yards run by the receiver to the thrower." You'd say I was nuts.

I'd say, "Well, it takes a special kind of talent for a passer to get a lot of yardage after the catch (YAC). I won't be able to prove it, in fact, I won't have any evidence for that statement at all, but I still think our primary measure of a passer should include all those yards." I'd be laughed at.

Here are the QBs from 2007 who led the league in percent of their passing yardage as YAC: Croyle, Testaverde, Greise, Harrington, Favre, McCown, Losman, and Lemon. The 2006 list includes Brunell, Carr, Favre, (Rob) Johnson, and (Alex) Smith. There's isn't a single guy on that list who we can call a legitimate starter.

The 2008 season's list of leaders in %YAC include Cassel, O'Sullivan, Campbell, Favre (again), Losman, and Wallace. But Matt Cassel is good, right? Maybe not. Keep in mind how good the team around him was. He was handed the keys to a Ferrari. If a QB racks up his passing yards with YAC, he's either throwing lots of short check-downs and screens, or he has spectacular receivers--or both. Neither is necessarily an indication of a particularly skilled passer.

If we throw away all the YAC and look underneath, what do we have left? I call it Air Yards (AY). It's the distance forward of the line of scrimmage a pass travels. Although it's not a perfect measure of a passer, I think it makes a lot more sense than crediting Donovan McNabb with 71 yards and a touchdown for a 1-yard screen pass to Brian Westbrook.

I agree with this. It's just one measure, and of course accuracy does help lead to more YAC and even screen passes take some athleticism and dexterity to pull off, but the analysis here indicates that we should not give QBs too much credit.

The other reason I like it is because it heightens accountability for yards after catch yards for receivers. If receiver X gets a lot of YAC and receiver Y doesn't, it might be a function of the offense they play in or the types of routes they run, but you nevertheless get a way to compare receivers and put the burden on them: either he's getting yards after the catch or he isn't, and the team should play a guy who gets them. Now, part of Brian's analysis here seems to indicate that it is QBs who drive this as much as anything else -- if a QB can't complete it downfield he'll inflate YAC all around with dump-offs. But, as I said, it's a fascinating statistic as a way to unpack yards per attempt, which is still the best overall metric of a passing offense.

2. Assorted Links

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Carl said...

I'm not totally convinced that YAC has no correlation with QB skill without some additional statistical analysis. Clearly most of it is up to the receiver, but the QB's placement of the ball can have a huge impact on the YAC potential of any given reception.

Grif said...

Re: Overtime

I have a friend who suggested the first team to score 6 points wins. I have yet to think of a strong reason to completely dismiss that as a bad idea.

Also, I don't think anyone would suggest YAC has no correlation with QB skill. But I think it gives less undeserved credit to the receiver than total yards gives to the QB. And, the point is, it just makes a whole lot more sense to give the receiver the YAC and the QB the Air Yards.

Anonymous said...

The single biggest factor in passing success is pass protection. ANY statistical metric seeking to compare QBs is fatally flawed if it assumes (as they must) that the QBs have equal quality pass pro (and receivers for that matter).


Anonymous said...

I couldn't disagree with you more on air yards. YAC is precisely what makes great QBs. High school accuracy is getting the ball in the general vicinity of the receiver, college accuracy is hitting the receiver, professional accuracy is the difference between hitting the receiver on the right or left shoulder.

A few years ago there was a bit where Steve Young talked about this exact thing, leading the receiver towards the running lane. If Young, or Montana for that matter, threw the ball behind rice it wasn't because the throw was off the mark. It was because they wanted Rice to turn back in because that is where the running lane was. And rice almost always went there the ball placement told him to go.

Now do all QB's have this level of skill? No. But good QB's do. Good QB's know how to lead their receivers to the running lanes with the placement of their passes and as such YAQ is just as much a measurement of the QB as it is the WR. I don’t care how good the WR is if the QB is laying them out to dry he wont have much YAC.