One of the most lamentable aspects of being a college football fan as far as I'm concerned has long been the lack of quality stat keeping, as well as analysis. Matt Hinton (currently Dr. Saturday) and Chris at Smart Football are great, and if CFB Stats didn't exist, this post wouldn't exist, but it ain't no Fangraphs and those fellas ain't quite Tom Tango, who literally wrote The Book on baseball. Not that it's a fair comparison.
I bring Tango up because his stat wOBA inspired this post. wOBA (weighted On Base Average) is basically on base percentage gone plaid. Instead of dividing times on base (1B+2B+3B+HR+BB+HBP+ROE) by plate appearances, you decide how valuable in terms of runs each of those individual events are and then proceed (hence weighted). OBP is transformed into runs per plate appearance. Multiply times total PAs and you have the runs that batter was responsible for in that season. And scoring (or preventing) runs are the bottom line in baseball. In sum: bases get you runs get you wins. In football, it looks like this:
Yards - Turnovers = Points
This isn't exactly groundbreaking. It's a fundamental assumption behind Dr. Saturday's Life on the Margins, iirc, and I'm pretty sure this is what I'm going to find in Pete Palmer's Hidden Game of Football if and when it eventually ships to a2. And it's sorta-kinda what David Romer did, though not nearly exhaustive. The theory is good. The actual arithmetic is kind of annoying and is summarized in the following paragraph. Feel free to skip to the part where we find out just how crippling the impact of Nick Sheridan was and how much worse it could have been.
The key to being able to do this yourself is to figure out yards and turnovers in terms of points. I ripped the drive logs of every Big Ten conference game in 2008 from Yahoo. That'll give you yards/point, which came out to about 15. Then I plotted, in buckets of 10 yards, the percent of drives that resulted in a TD or FG based on the drive starting field position, except the last 30 yards which I averaged at the opponent's 15 due to relatively few samples.* This gives you average expected points based on field position. That plus average field position equals the average value of a possession, which is what you lose in a turnover. Not only that, but you give expected points to your opposition. According to my math, an INT was worth about -4 points. Thus points per throw is (Yds/15 + INTs*4)/attempts.
Feel free to comment
I Am Not An Expert. If my math is off, then suggest different constants/methods. They pass the sniff test to me; I ran assorted regressions on excel to test assumptions and it looked right. I'd be glad to share the drive chart database. Onward...
The Part Where We Find Out Just How Crippling The Impact Of Nick Sheridan Was
It's sorted by pts/attempt, the relevant measure. Average was .33. Mr. Sheridan was dead last with those over 50 attempts with .15 points per attempt. An all around average team wins 4 games. The results indicate that an all around average team that replaced its average quarterback with Nick Sheridan would win 2 (converting to wins over average is easy enough). But it would also have tremendous team chemistry and at least one valedictorian. Wins aren't everything.
Also, check out Terrelle Pryor's numbers. Remember, this is just per throw. Rushing and sack yards are not included, nor is it defense adjusted. Having rewatched the Texas and Michigan games in HD (being able to see the d-backs helps), I was impressed. Tressel used the threat of Wells inside and Pryor's skills when bootlegged on the edge to great effect. The playbook seemed cut down, but his athleticism made it work. The sack numbers (scroll right in the g-doc) and somewhat inconsistent mechanics are the most glaring issues, but they were exaggerated by a bad pass blocking unit in front of him. In conclusion: barring injury, Pryor is going to be a terror. Surprise! Rivals #1 overall prospect in 2008 is projected to dominate. At least he'll probably be gone after his junior year.
*It's a shortcut and it probably understates how valuable possessions that start inside the 15 are. I actually think inside the 15 the function is probably no longer linear. I'm also sorry that this is isn't the most thorough or transparent presentation. It's a start though.