One of the very first things PFF was able to learn and push was how overrated sacks are as a statistic or, more specifically, as a means of measuring pass-rush talent. But the first day of the 2021 free agency period suggests NFL teams are still not much closer to learning the lesson.
Sacks are important, and they’re the play that all pass-rushers are chasing, but they are a lousy measure of pass-rush performance, and therefore future performance, for a couple of reasons.
Sample size is the first and most obvious issue. Edge rushers can play upwards of 1,000 snaps in a season. The difference between a great season (15 sacks) and an underwhelming one (five) is 10 snaps — 1% of that player’s season.
Instead, you can significantly increase the sample size if you focus on total pressures instead of just sacks, and you can increase it even further if you look at snaps where the pass-rusher defeated his block but the ball came out before he could pressure the quarterback. PFF tracks all of those plays, and they are included in our pass-rushing grades, which is why both grades and total pressures are a much better predictor of future sacks than how many sacks a player has.
The second issue is that not all sacks are created equally, particularly if we use the NFL’s official numbers.
A sack can result from a variety of different qualitative wins from the pass-rusher, which range from just being the closest player to the quarterback as he runs himself out of bounds to splitting a double-team and destroying the pass-blocking in quick order for an impact play.
With all of the other variables involved, it’s easy for those plays to quickly build up and create a picture of a player’s season that doesn’t necessarily accurately reflect the picture in our minds of what a 10- or 15-sack season looks like.
A great example of this is Trey Hendrickson, who is universally being talked about as “one of the NFL’s leaders in sacks last season.” The only issue is that the description comes without any context to that data point. Hendrickson sacked the quarterback 14 times last season (13.5 official sacks) — a figure that more than doubled his previous career-high, a warning signal in and of itself — but those sacks look less impressive if we look at pressure, grade and the quality of those sacks.
Trey Hendrickson: Pass-rush stats and rank in 2020 (regular season only; among edge rushers with 250 or more pass-rush snaps)
|Clean-up, pursuit and unblocked sacks||11||1st|
|% of sacks due to clean-up, pursuit and unblocked||78.6%||10th*|
|PFF Pass rush grade||78.0||15th|
|Pass-rush win rate||16.8%||16th|
* Rate among edge defenders with three or more sacks
Of the 14, a massive 11 (78.6%) were either unblocked, clean-up or pursuit plays. That’s not to say that those plays are necessarily bad, but they require less transferable, repeatable pass-rush skill than beating blocks to generate pressure does.
Only T.J. Watt tallied more sacks among edge rushers than Hendrickson last season, but the former Saint ranked just 21st at the position in terms of total pressures with 49. Consequently, he ranked only 15th among his peers in PFF pass-rushing grade. Hendrickson was solid, but he was flattered to a huge degree by one statistic that remains too large in people’s minds.
Another player inflated to a similar degree is Bud Dupree, who has 22 sacks to his name over the last two seasons despite missing five games through injury in 2020.
Dupree has a lot working in his favor in addition to the draw of sacks — he is also a spectacular athlete and a former first-round pick, two more aspects that have outsized value when it comes to chasing available talent. But like Hendrickson, Dupree’s stats don’t hold up as well under closer scrutiny.
At the time he went down injured, 61% of his total pressures were either unblocked, clean-up or pursuit plays. Since the start of the 2018 season, 47.9% of his pressures have come that way, one of the highest marks in the league among all edge rushers.
Dupree gets a lot of those plays because he does have a high motor and is a great athlete, but the percentage speaks more to how little he is winning blocks despite being put in a position to be one-on-one a lot because of the talent around him in Pittsburgh. Dupree was signed to be an answer to Tennessee’s anemic pass-rush, but he is unlikely to be that answer, given his tape history beyond the box score numbers.
First, Dante Fowler Jr. managed a 15-sack season having totaled 10 in the two seasons either side of that year combined, but it earned him a big payday with the Falcons. This season, Leonard Floyd was able to parlay his 13-sack year into a huge raise with the Los Angeles Rams. Floyd notched 10 more sacks than his previous season with the Chicago Bears, but his PFF pass-rush grade only improved five grading points and was still only slightly above average. These players didn’t become dramatically better pass-rushers, but you might have thought so if you only looked at sacks and ignored the outside factors affecting that number.
Then we come to Carl Lawson, the top-ranked edge rusher on PFF’s free-agent rankings heading into the week. Lawson has a lower average-per-year payout than Floyd or Dupree but has been by far the best pass-rusher of this group over the past few seasons — it just hasn’t yet been reflected in sacks.
Lawson ranks 15th among edge rushers over the last two years in total pressures, but he has rushed the passer significantly fewer times than some of the players above him. His pass-rush win rate over that same period ranks him above the likes of Khalil Mack, Nick Bosa and Shaquil Barrett. He ranked fourth in the league in 2020 alone, but because Lawson has just 22 career sacks over four years, he is seen by many to be a lesser pass-rusher. His PFF pass-rushing grades have consistently been good, topping 80.0 in two of his four seasons, and his pressure rate has been impressive, with 64 of them last season alone.
Lawson still earned a healthy contract and landed in a great situation under Robert Salah in New York, but the data says that Lawson should have been a much more coveted player than the other pass-rushers he was battling it out with, but too many people are still far too blinded by sacks, and it is skewing their evaluation of pass-rushers.