Recently, I began constructing a passer rating system that, to the greatest degree possible, includes performance variables controlled by the quarterback alone and avoids redundant use of variables that measure the same attribute. This improved system includes completion percentage, interception rate, and sack yards per attempt. The previous two posts discussed completion percentage and interception rate. This post will examine sacks. Each of the stats used in the rating system are computed in terms of how many wins they add, on average, to a QB's team over the course of a season. The wins added are based on the previously established regression model based on team efficieny stats.
More and more, I'm coming to realize that sacks are far more dependent on the quarterback than on his pass protection. A quarterback's mobility, release, decision-making, and pocket presence all are critically important. I'm using sack yardage rate instead of total absolute sacks for two reasons. First, the number of pass attempts must be accounted for. We would expect a QB with more pass attempts to be sacked more often than a QB who passes less often, given equal abilities to prevent sacks. Second, sack yards yield more information about the QB than sacks alone. Some QBs have fewer sacks, but because they often gamble by scrambling deep in the backfield, they give up large numbers of sack yards. Does the QB tend to step up in the pocket or drift backward? As you'll see, some of the QBs considered the most mobile actually give up some of the most sack yards.
The table below lists each quarterback with at least 100 pass attempts in 2006, their sack yards, and their sack yardage rates (sack yards per pass attempt). The column labeled "Sk Yd Rate > Avg" is the sack yardage rate above (or below) league average. The next column, "+Sk Yd Wins" lists the wins added based on sack yards for each quarterback. The list is sorted in order of best to worst.
|Player||Sk Yds||Sk Yd|
|SkYdRate > Avg||+Sk Wins|