Per PFF
Sacks are important and worth about two points for a defense. They usually end drives and often force turnovers. They are the ultimate goal of all pass rushers and rightly the most valuable non-turnover play for a defender.
But if you want to know how good a pass rusher is, and how good he’ll likely be the following season, look at his pressure rate. We at PFF define a pressure as a sack, a hit or a hurry on a quarterback, with the best pass rushers able to generate a pressure on 15 to 20 percent of their pass-rush snaps. For a pass rusher with 500 pass rushes during a season, you’re talking about 75 or so plays, versus just 10 sacks.
Generally speaking, “finishing” pressure with a sack isn’t really a trait a pass rusher possesses per se. If you want to predict a player or team’s sack total one year, use his or its pressure rates from the previous season. A 20 percent decline in a player’s sack total from 10 to eight, for example, is mostly noise. But a 20 percent dip in a player’s pressure rate from 50 to 40 is less so. Process over results
