STDL: Week 13 - Broncos at Vikings, plus Tebow stats

We're going to change things up a little bit with Week 13's STDL. As I mentioned last week, I'd been thinking of switching the passing numbers here to NY/A (Net Yards per Attempt) from ANY/A (Adjusted Net Yards per Attempt) since NY/A is better at predicting future results, which is the whole point of this column. NY/A adds sack data to plain old YPA (Yards per Attempt), while ANY/A adds the weight of touchdowns and interceptions to the mix. Why is NY/A more predictive, while ANY/A is more retrodictive (better at explaining why something already happened, rather than what's likely to happen next)?

Touchdowns and interceptions are more random than YPA. Not random, mind you, just more random than YPA - in other words, if your offense is effective at moving the ball down the field, it's likely to score more than an offense that doesn't move the ball well. Naturally, the 2008 Broncos would stand as a stark exception (2nd in Yards per Play, 16th in Points). Of course, this means I need to reconsider whether to keep touchdowns in with the rushing data. That could be next week's tweak...

Plus, we'll take a look at how Tim Tebow stands in relation to the other QBs in the league via NY/A and ANY/A data, but with rushing stats baked in! As always, there'll be something in it for Tebowmaniacs and Tebow Skeptics alike.

As always, an explanation of the figures:

• NY/A Differential: This is a marriage of PFR's NY/A (Net Yards per Attempt) and CHFF's Passer Rating Differential. NY/A takes the all-important Yards Per Attempt and adds sack data into the mix to provide a clearer picture of a passing game's impact. NY/A Differential is simply a team's NY/A minus the NY/A they've allowed on defense. In other words, how well Denver passes the ball minus how well they defend against the pass.
• ARY/A Differential: This is a team's efficiency rushing the football minus the efficiency of their defense in stopping the run, and it factors touchdowns in to provide a better measure than a simple Yards Per Attempt stat. Well, for now - we'll likely change this next week, as mentioned above.
• TO Differential: Takeaways minus giveaways. If you need help with this one, you must be a Raiders fan and probably refer to this as a ratio.
• Net Field Position: This is a team's average starting field position in terms of yards, minus the average starting field position they allow their opponents.
• Strength of Schedule: This is each team's strength of schedule as viewed through the prism of PFR's SRS (Simple Rating System).

Looks like a pretty even matchup, especially when considering that Denver's negative TO Differential was a gift bestowed on Tebow by Kyle Orton, Kansas City Chief. As you can see, the biggest problem for Denver is that Minnesota is even better than they are at both running the ball (5.82 to 5.08) and stopping the run (4.15 to 4.34). Both key injuries (Von Miller and Adrian Peterson) will have a major impact today, as both players will miss the game. But due to the absence of Peterson, I've changed my pick from Minnesota to Denver (we originally make our picks on Thursday).

QB Stats

So everyone's been clamoring for some QB data that adds rushing stats to the picture, and this is as good a time as any to present them - Tim Tebow is likely to surpass the threshold for pass attempts today that will qualify him for leaderboards on QB rate stats. Okay, maybe this means that next week would be more appropriate, but whatever. Let's do it anyway.

Let's start out by establishing that if Tebow had enough pass attempts to qualify today (he's just short), his 80.5 traditional QB Rating would be good enough for 21st in the NFL, just behind Philip Rivers and a touch above Michael Vick. Not bad company, no matter how rough their seasons are going and considering it's Tebow's second season.

First, the math:

We're basing our formula on the work already done by Chase Stuart for the PFR Blog (he's now at Chris Brown's SmartFootball.com after PFR closed their blog) but adding some tweaks. Here's the original formula:

[(PYD + 20*(PTD + RTD) - 45*INT - SKYDLST - 35*(FUM-FumRec)) / (ATT + SK +RTD)]

If you're wondering, the values being used to bake in Touchdowns, Interceptions and Fumbles were based upon the work done by the authors of The Hidden Game of Football, which had originally valued a Touchdown as being worth 10 yards. Stuart explains the increase to 20 yards here. Here's the formula we're going to use for our Adjusted Net Yards per Touch:

[(Pass Yds + Rush Yds + Rec Yds - Sk Yds + 20*(Pass TD + Rush TD + Rec TD) - 45*INT - 35*FUM) / (Pass Att + Rush Att + Rec + Sks)] 

The differences between our formula and that used by Stuart at PFR are as follows:

1. We've added rushing and receiving yards, and receiving touchdowns. As for the receiving stats, hey - you never know right?
2. We're going with straight fumbles rather than net fumbles, because we're treating all fumbles as negative events - whether or not a team recovers its own or not. As we all should know by now, fumble recoveries are random events. As for how this will affect one player over another, it really won't do so very much - perhaps only Matt Moore this season, because he's put it on the ground a whopping 3.4% of the time he's touched it.

In the following charts, I've included everyone who's attempted at least 100 passes so far this year, which is 39 quarterbacks in total. First, let's look at ANY/T which will be one of those metrics (like ANY/A) better at telling a retrodictive story than predicting the future:

2011 QB Data through Week 12, sorted by Adjusted Net Yards per Touch

These results largely mirror traditional QB Rating, with a few notable exceptions. You'll recall that on Friday we were talking all about Completion % and how traditional QBR (and thus CHFF's Real QB Rating) vastly overcredit it. So, the players that drop in our rating (mainly due to a lack of TD passes) are Alex Smith and Matt Moore, at quick glance.

Tebow ranks 19th among the 39 quarterbacks, largely on the strength of his excellent 11-to-6 ratio of TDs to picks and fumbles. I'll probably introduce a measure of QB's negative plays next week (Interceptions, Sacks, Fumbles) but just know for now that Tebow ranks better than average there.

Next, let's take a look at Net Yards per Touch, which is as follows:

[(Pass Yds + Rush Yds + Rec Yds - Sk Yds) / (Pass Att + Rush Att + Rec + Sks)] 

This is simply a matter of adding rushing and receiving stats to NY/A. Here are the results:

2011 QB Data through Week 12, sorted by Net Yards per Touch

Tebow ranks 36th out of 39 quarterbacks via this measure, which means he's not efficient in terms of yardage. This number will have to improve significantly over time, because it is highly unlikely (impossible?) for him to continue to be so inefficient but still score as many touchdowns and have as few negative plays as he's had. Obviously, an improvement in his overall passing would go a long way to accomplish this.

In the end, Tebow has been far below average in NY/T but is much closer to being average at ANY/T, and he'll likely need to boost his NY/T to even maintain his ANY/T where it is. I hope this at least serve to answer some questions, and of course we'll have a clearer picture the more Tebow plays.