Not all 10-sack seasons are equal in the NFL. Opportunity matters. The likelihood of bringing down a quarterback is a lot higher on a third-and-10 blitz against Daniel Jones than a four-man rush on first-and-10 against Drew Brees. Those chances are not distributed evenly.
That's why we're introducing a new metric we're calling expected sacks. The idea is to determine the likelihood of an average pass-rusher recording a sack on each play, based on the factors around him. The factors for each pass-rusher on every play are:
What position he played
Whether he was double-teamed
Down and distance
What the season sack rate of the quarterback he was facing was
How many players rushed the passer on that play
How many of his teammates earned a pass rush win on that play
What the season pass rush win rates of his teammates were
The game's win probability
The sack expectations produced for every play can then be added up for the season, allowing us to see which players had better opportunities than others, and who beat (or fell short of) their expectations. Double-teams and pass rush wins are ESPN metrics powered by NFL Next Gen Stats data.
Let's focus on the free-agent pass-rushers and evaluate the context of their 2020 sack totals -- along with other advanced pass-rushing metrics -- to get a fuller picture of their 2020 seasons beyond the simple number of plays they brought down the quarterback. We'll also include J.J. Watt, who just signed with the Cardinals, and see whether or not Arizona got a productive player.