March 31, 2009

Zack Lehatto
USCFootball.com Staff

	Practice Period
		Aaron Corp	Mitch Mustain	Garrett Green	Matt Barkley
	7-on-7	123.0	157.75	106.50	97.80
	11-on-11	128.43	71	90.14	123.33
	Spring Rating	126.17	114.38	96.09	111.73

QB Metrics ? A Breakdown

USCFootball.com is looking for a way to breakdown USC's quarterback battle as thoroughly as possible. One half of the equation is the feel that the staff gets from practice, the intangible things each quarterback does to rally the team around them and what the coaches say about their performances.

The other half is, well, the equation. More specifically, we've decided to follow every throw that each quarterback makes to come up with a USCFootball.com QB-Rating.

The QB-rating will be broken down in a number of ways, but it is based off of the NCAA QB-rating. The rating is a function of passes completed, attempted, yardage, interceptions and touchdowns. The formula does not account for sacks, fumbles, QB-scrambles or pass interference. However, the formula we have devised considers a sack or fumble the same as a pass attempt. So, while it does not value it heavily, it is in there in some capacity.

Yardage statistics at practice are limited at best, and since the data we are collecting is only available by one of us being there to interpret the distance, it is broken down into three levels of success: Short, Medium, Long. Short includes dump passes, checkdowns, screens, etc. Medium and Long are self-explanatory. The resulting formula for this, if Short is 1 and Long is 3, with distance being X, is:

(X-1)7.5 + 5 = Yardage

Therefore, Short passes count for 5 yards, Medium 12.5 yards and Long passes are 20 yards. Obviously, this is not 100-percent indicative of their success, but it is impossible to account for it any other way.

The second factor that we're accounting for is the level of competition that a QB is playing against and the quality of teammates that they are playing with.

The defensive values are broken down into three categories, first-team, second-team and third team. The QB-ratings get a 20% bonus if they are playing against the first team, no bonus/penalty against the second and a 20% penalty on their rating if they are going against the third team defense.

The offensive value is the same system, but reversed. A 20% penalty for playing with the first-team, no penalty for second and a 20% bonus for third-team offense.

The way that the offensive/defensive value data is collected is subjective, and based upon the staff's opinion of what players are on the field. For times when the level of players is too ambiguous, the ratings default to second team.

The third factor that we have accounted for is the difference between 7-on-7 drills and 11-on-11 scrimmage. Naturally, a quarterback is going to be more successful when there is no pass rush, so it is necessary to break up this data. However, the 7-on-7 data still provides a picture of how successful the QB is compared to his teammates.

The end result of all this data are six unique QB-ratings:

QB-Rating: Takes into account all of the data, unadjusted for offense/defense or type of drill.
QB-Rating Adjusted: Cumulative data adjusted for offense/defense, no adjustment for drill/scrimmage.
QBR?11s: Only 11-on-11 counts, with no adjustment for offense/defense.
QBR-11: Adjusted: Only 11-on-11, offense/defense accounted for.
QBR?7s: Only 7-on-7 counts, with no adjustment for offense/defense.
QBR-7 Adjusted: Only 7-on-7, offense/defense accounted for.


Ultimately, the QBR is just another tool to evaluate the quarterback battle. There is a lot of behind-the-scenes action that we are not entirely privy to.

It should also be mentioned that it is a limiting formula because of the yardage, and does not allow the quarterbacks to approximately exceed 600, whereas the actual NCAA formula allows for a rating close to 1,300.

So, please, do not compare the rating directly to what actual NCAA QB-ratings are. This is only as a gauge between current USC quarterbacks.

Stay tuned to USCFootball.com for an update after every practice and further breakdowns of specific situations and circumstances.