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 YdRate SkYdRate > Avg +Sk Wins Peyton Manning 86 0.15 -0.28 0.44 Tim Rattay 18 0.17 -0.26 0.41 Steve McNair 84 0.17 -0.26 0.41 Drew Brees 105 0.18 -0.25 0.39 Jeff Garcia 40 0.21 -0.23 0.36 Brett Favre 134 0.21 -0.22 0.35 Byron Leftwich 48 0.25 -0.18 0.29 Jason Campbell 55 0.26 -0.18 0.28 Rex Grossman 142 0.28 -0.15 0.24 Joey Harrington 116 0.29 -0.15 0.23 Chris Simms 32 0.29 -0.14 0.22 Philip Rivers 144 0.30 -0.14 0.22 Tom Brady 175 0.32 -0.11 0.17 Jake Plummer 111 0.33 -0.10 0.16 Chad Pennington 172 0.33 -0.10 0.16 Vince Young 129 0.34 -0.10 0.15 Mark Brunell 92 0.34 -0.10 0.15 Eli Manning 186 0.34 -0.09 0.15 Tony Romo 124 0.35 -0.09 0.14 Jake Delhomme 167 0.37 -0.07 0.10 Matt Leinart 158 0.40 -0.04 0.06 Damon Huard 106 0.41 -0.03 0.04 Bruce Gradkowski 146 0.41 -0.02 0.03 Donovan McNabb 140 0.42 -0.02 0.03 Carson Palmer 233 0.42 -0.01 0.02 Alex Smith 202 0.42 -0.01 0.02 Brad Johnson 200 0.43 -0.01 0.01 David Garrard 119 0.46 0.02 -0.03 David Carr 240 0.50 0.06 -0.10 Derek Anderson 66 0.53 0.09 -0.15 Seneca Wallace 83 0.54 0.10 -0.16 Ben Roethlisberger 280 0.54 0.11 -0.17 Matt Hasselbeck 229 0.57 0.13 -0.21 Jay Cutler 85 0.57 0.13 -0.21 Kurt Warner 104 0.57 0.14 -0.22 Trent Green 127 0.57 0.14 -0.22 Marc Bulger 366 0.57 0.14 -0.22 Drew Bledsoe 107 0.58 0.14 -0.23 Jon Kitna 388 0.59 0.15 -0.24 Charlie Frye 262 0.60 0.17 -0.26 J.P. Losman 332 0.70 0.26 -0.41 Michael Vick 303 0.70 0.27 -0.42 Andrew Walter 256 0.80 0.36 -0.57 Aaron Brooks 174 0.80 0.36 -0.57 Daunte Culpepper 150 0.97 0.53 -0.84 Average 155.9 0.43