Pass pressure comes in different categories. The quarterback sack is the ubiquitous play, but at Football Outsiders, we track other methods of disrupting passing plays. There's the quarterback hit, in which a defender knocks the quarterback to the ground during (or after) the throw. Then there's the quarterback hurry, which we track with the Football Outsiders game charting project. These numbers are also adjusted based on individual game charters, but we end up with fairly accurate indicators of how many pressures either cause a hurried throw, or prompt offensive holding penalties. Hurries are the most common pass pressures -- in 2009, there were 1,106 quarterback sacks, 1,522 quarterback hits (including on plays cancelled by penalties) and 3,268 adjusted hurries.
Hurries aren't as immediately effective as sacks, in that they don't end plays, but they do affect quarterback play. Last season, the average pass play yielded 6.2 yards and a mean DVOA (defense-adjusted value over average, FBO's per-play efficiency metric) of 13.6 percent. When the defense hurried the quarterback, the average pass play gained 5.0 yards and averaged a DVOA of minus-16.2 percent. There are those rare quarterbacks, like Aaron Rodgers, Donovan McNabb and Ben Roethlisberger, who produce well when under that kind of pressure, but the average stats tell the value of the hurry.