atlantacowboy
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I post PFF grades just about every week. So, I think those that are interested and comment on those threads should at least understand the metric. Why does Zeke always grade poorly? How the heck is Diggs season grade a 54 making him one of the worst graded CBs in the NFL , yet he leads the league in INTS. I copy pasted PFF's explanation for these anomalies here you have a huge disparity between a players PFF grade and the perception of fans whose opinion are molded by stats.
GRADES VS. STATS
We aren’t grading players based on the yardage they rack up or the stats they collect. Statistics can be indicative of performance but don’t tell the whole story and can often lie badly. Quarterbacks can throw the ball straight to defenders but if the ball is dropped, you won't see it on the stat sheet. Conversely, they can dump the ball off on a sequence of screen passes and end up with a gaudy looking stat line if those skill position players do enough work after the catch.
PFF grades the play, not its result, so the quarterback that throws the ball to defenders will be downgraded whether the defender catches the ball to notch the interception on the stat sheet or not. No amount of broken tackles and yards after the catch from a bubble screen will earn a quarterback a better grade, even though his passing stats may be getting padded.
The same is true for most positions. Statistics can be misleading. A tackle whose quarterback gets the ball out of his hands quicker than anybody else may not give up many sacks, but he can still be beaten often and earn a poor grade. Receivers that are targeted relentlessly could post big-time numbers but may offer little more than the product of a volume-based aerial attack.
Here’s a great example from the 2016 season as to why grades and stats may not match up:
In 2016, Atlanta Falcons edge rusher Vic Beasley led the NFL in sacks in a breakout season for the NFC Champions, but he was only the 31st-ranked edge rusher in terms of PFF pass-rushing grade. Here are some of the things to note about how Beasley rated in our system:
Not all sacks are created equal
Beasley sacked the quarterback 16 times, but eight of those sixteen were either unblocked or clean-up sacks that owed more to somebody else flushing the quarterback towards where Beasley was than they did to him beating a blocker to make the play. PFF grading takes into account the quality of the play made to get the sack, and excellent plays to defeat blocks will be graded higher than sacks where the quarterback just happened to be flushed past a player as he was being blocked only to get taken down.
Pressures matter
All pass-rushers are trying to sack the quarterback, but even the best will only do so on around three percent of their snaps on the field. Hits and hurries combine with sacks to form a much more robust picture of total pressure generated.
Pressure that does not result in a sack is important too, as just pressuring the quarterback sees an average drop in passer rating of 32.0 points from 94.4 to 61.8 over the past 10 years. That’s the equivalent of turning Ben Roethlisberger into Blaine Gabbert just by hurrying him in the pocket.
Beasley led the league in sacks, but he was just 18th even among edge defenders when it comes to total pressures. Compare that to a player like Oakland’s Khalil Mack who led the league with 96 combined sacks, hits and hurries, and Beasley has a significant deficit in total pressure.
When we used our analytics to run numbers to find out just how valuable pressure was compared to sacks, our Expected Points Added data showed that a sack is worth around 2.1 pressures of any other kind. So, a player like Mack would only need to have had an extra 11 hits or hurries to have added more value as a pass-rusher than Beasley despite having five fewer sacks over the season. Mack, in reality, had 40 more pressures, and so had a significantly higher PFF grade than Beasley.
Run defense matters
Mack’s overall grade of 95.2 was also far higher than Beasley’s 74.2 because Khalil Mack was one of the best run defenders in the game, capable of shedding blocks and knifing into the backfield to blow up plays. Beasley wasn’t nearly as accomplished in this area, an area that can get lost in all the talk of sacks but is counted in the PFF grading.
GRADES VS. STATS
We aren’t grading players based on the yardage they rack up or the stats they collect. Statistics can be indicative of performance but don’t tell the whole story and can often lie badly. Quarterbacks can throw the ball straight to defenders but if the ball is dropped, you won't see it on the stat sheet. Conversely, they can dump the ball off on a sequence of screen passes and end up with a gaudy looking stat line if those skill position players do enough work after the catch.
PFF grades the play, not its result, so the quarterback that throws the ball to defenders will be downgraded whether the defender catches the ball to notch the interception on the stat sheet or not. No amount of broken tackles and yards after the catch from a bubble screen will earn a quarterback a better grade, even though his passing stats may be getting padded.
The same is true for most positions. Statistics can be misleading. A tackle whose quarterback gets the ball out of his hands quicker than anybody else may not give up many sacks, but he can still be beaten often and earn a poor grade. Receivers that are targeted relentlessly could post big-time numbers but may offer little more than the product of a volume-based aerial attack.
Here’s a great example from the 2016 season as to why grades and stats may not match up:
In 2016, Atlanta Falcons edge rusher Vic Beasley led the NFL in sacks in a breakout season for the NFC Champions, but he was only the 31st-ranked edge rusher in terms of PFF pass-rushing grade. Here are some of the things to note about how Beasley rated in our system:
Not all sacks are created equal
Beasley sacked the quarterback 16 times, but eight of those sixteen were either unblocked or clean-up sacks that owed more to somebody else flushing the quarterback towards where Beasley was than they did to him beating a blocker to make the play. PFF grading takes into account the quality of the play made to get the sack, and excellent plays to defeat blocks will be graded higher than sacks where the quarterback just happened to be flushed past a player as he was being blocked only to get taken down.
Pressures matter
All pass-rushers are trying to sack the quarterback, but even the best will only do so on around three percent of their snaps on the field. Hits and hurries combine with sacks to form a much more robust picture of total pressure generated.
Pressure that does not result in a sack is important too, as just pressuring the quarterback sees an average drop in passer rating of 32.0 points from 94.4 to 61.8 over the past 10 years. That’s the equivalent of turning Ben Roethlisberger into Blaine Gabbert just by hurrying him in the pocket.
Beasley led the league in sacks, but he was just 18th even among edge defenders when it comes to total pressures. Compare that to a player like Oakland’s Khalil Mack who led the league with 96 combined sacks, hits and hurries, and Beasley has a significant deficit in total pressure.
When we used our analytics to run numbers to find out just how valuable pressure was compared to sacks, our Expected Points Added data showed that a sack is worth around 2.1 pressures of any other kind. So, a player like Mack would only need to have had an extra 11 hits or hurries to have added more value as a pass-rusher than Beasley despite having five fewer sacks over the season. Mack, in reality, had 40 more pressures, and so had a significantly higher PFF grade than Beasley.
Run defense matters
Mack’s overall grade of 95.2 was also far higher than Beasley’s 74.2 because Khalil Mack was one of the best run defenders in the game, capable of shedding blocks and knifing into the backfield to blow up plays. Beasley wasn’t nearly as accomplished in this area, an area that can get lost in all the talk of sacks but is counted in the PFF grading.
