FanPost

A Proposed Change to Talk About PFF Player Grades - from Buzzy

GGN member Buzzy made an excellent point in one of the threads recently regarding PFF grades. He included snap numbers when talking about overall grades for safeties, alluding to a huge hole in much of the use of these grades. Because they are called "grades" people think of them as the kind of qualitative grade that is given by a teacher or a football scout. Your an "A" or a "B" kind of player. But that really isn't how these grade values work. These are cumulative numbers, both positive or negative. They are additions of earned points. Just because you can earn negative values doesn't change this really. And it stands to reason that if Player A earned a +15.5 season rating in 652 snaps, and another, Player B earned the same in 1032 snaps, Player A was the far superior player at producing a net positive result (at least in the eyes of the respective graders). The problems of the grading itself is another matter altogether. He was impacting the game positively, according to Pro Football Focus at a much higher rate. This is the answer to the lazy interpretation that reads the PFF Grades as: How Good Is This Player? And Was This Player Better than That Player?

The Proposed Change

PFF isn't going to change how they show things on their site, but we at GGN can change a little how we talk about their grades. If there is going to be talk about them - something I don't really favor all that much - we should be looking at these comparative grades as cumulative totals judged by the rate at which those totals are produced, not just as qualitative marks given at season's (or game's) end. This means that a stat like: total snaps / overall grade would tell us how many snaps it took to produce a +1.0 increase in grades (for high ranking positively graded players). Simple formula like these work.

overall grade:

snaps / grade value

pass grade:

Thrown Ats (TAs) / grade value

run grade:

attempts / grade value

Here are some examples of how this changes things the PFF Grade Ratio next to the PFF Grade:

Safety Overall Grades:

Name Team PFF Grade Ratio PFF Grade
Will Hill NYG 50.1273885350318 15.7
Devin McCourty NE 55.5614973262032 18.7
Jairus Byrd BUF 65.2525252525252 9.9
Eric Berry KC 71.6551724137931 14.5
T.J. Ward CLV 77.5172413793103 14.5
Troy Polamalu PIT 89.5901639344262 12.2
Donte Whitner SF 89.8260869565217 11.5
Eric Weddle SD 90 11.3
Earl Thomas SEA 137.6 7.5
Michael Griffin TEN 152.5 6
Glover Quin DET 153.582089552239 6.7
Antrel Rolle NYG 156.081081081081 7.4
Kam Chancellor SEA 168.852459016393 6.1
Eric Reid SF 213.404255319149

4.7

Rashad Johnson ARZ 214.333333333333 3

We see for instance that Byrd graded out much better overall than the straight grade would show. Instead of the 9th best safety, he is the 3rd. And Berry showed better than Ward despite having the same grade.

For Safeties in Coverage you see this:

Name Team PFF Grade Ratio PFF Grade
Devin McCourty NE 1.91489361702128 14.1
Jairus Byrd BUF 2.31578947368421 9.5
Earl Thomas SEA 2.52252252252252 11.1
Chris D. Clemons MIA 2.91666666666667 7.2
Will Hill NYG 2.98076923076923 10.4
Troy Polamalu PIT 3.45323741007194 13.9
Donte Whitner SF 4.48598130841122 10.7
Glover Quin DET 4.77611940298507 6.7
Eric Berry KC 5.04 12.5
Shiloh Keo HST 5.27777777777778 3.6
Louis Delmas DET 5.92592592592593 5.4
Eric Weddle SD 6 9.5
Rahim Moore DEN 6.66666666666667 3.3
Rashad Johnson ARZ 7.25 4
George Iloka CIN 7.64705882352941 3.4

Byrd was the 7th best coverage safety by overall PFF grade, but by grade ratio he actually was the 2nd best. In fact he was producing a positive +1.0 grade at nearly twice the rate of the 7th best coverage safety. A pretty significant difference. Chris Clemens was the 4th best safety, and not the 9th best, again, twice as productive as the 9th best safety by Ratio.

a note: This comparison of safety grades and ratios also points to a significant weakness in PFF grades. When in direct coverage the top safeties are experiencing +1.0 grade changes about every 5 plays or so, but overall they are experiencing +1.0 grade changes around every 100 plays or so. This suggests that about 95% of the time their performance is falling out of the focus of the grading system. This hints to one of the larger problems with how PFF grades are read. The number quickly brands a player comprehensively, while much of the quality of that player can simply fall out of the purview of the grader.

Wide Receivers Overall Grades ranked by PFFR

Name Team PFFR PFF Grade
Brandon Marshall CHI 26.8096514745308 37.3
Julio Jones ATL 37.7215189873418 7.9
Marvin Jones CIN 39.6428571428571 14
Calvin Johnson DET 40.5777777777778 22.5
Antonio Brown PIT 41.7241379310345 23.2
Randall Cobb GB 43.5897435897436 7.8
Anquan Boldin SF 46.4245810055866 17.9
Jordy Nelson GB 46.4978902953587 23.7
Andre Johnson HST 51.0606060606061 19.8
Marques Colston NO 51.9047619047619 14.7
Alshon Jeffery CHI 52.0320855614973 18.7
Demaryius Thomas DEN 53.0985915492958 21.3
DeSean Jackson PHI 53.7234042553191 18.8
Reggie Wayne IND 54.8101265822785 7.9
Keenan Allen SD 57.1176470588235 17

And the WRs pass PFF Grade ranked by PFFR:

Name Team PFFR PFF Grade
Marvin Jones CIN 5.13333333333333 15
Jordy Nelson GB 5.74162679425837 20.9
Anquan Boldin SF 6.05911330049261 20.3
Keenan Allen SD 6.43312101910828 15.7
Antonio Brown PIT 6.88311688311688 23.1
Marques Colston NO 7.27891156462585 14.7
Calvin Johnson DET 7.32673267326733 20.2
DeSean Jackson PHI 7.4375 16
Doug Baldwin SEA 7.44897959183673 9.8
Randall Cobb GB 7.54716981132075 5.3
Brandon Marshall CHI 8.06122448979592 19.6
Golden Tate SEA 8.30357142857143 11.2
Julio Jones ATL 8.50746268656716 6.7
Reggie Wayne IND 9.04761904761905 6.3
Demaryius Thomas DEN 9.26174496644295

14.9

Running Backs Overall PFF Grade ranked by PFFR

Name Team PFFR PFF Grade
Darren Sproles NO 22.6086956521739 16.1
Andre Ellington ARZ 28.1632653061225 14.7
LeSean McCoy PHI 28.525641025641 31.2
LeGarrette Blount NE 28.6138613861386 10.1
Danny Woodhead SD 29.4736842105263 17.1
Giovani Bernard CIN 35.2247191011236 17.8
Joique Bell DET 37.2185430463576 15.1
Eddie Lacy GB 38.7078651685393 17.8
Jamaal Charles KC 38.8392857142857 22.4
Shane Vereen NE 39.6 7.5
Marshawn Lynch SEA 39.8378378378378 18.5
DeMarco Murray DAL 44.5161290322581 15.5
Pierre Thomas NO 48.9830508474576 11.8
Brian Leonard TB 49.8305084745763 5.9
Jacquizz Rodgers ATL 50.1136363636364 8.8

This is of note to Jet fans considering Sproles. Instead of McCoy walking away with Best Graded RB in the league in a romp, and Sproles showing at 7th, Sproles actually is the top rated PFFR Grade Producer in the league at RB, followed by Ellington who jumps up from 10th.

Here are just the RBs ranked by Run Grades alone, ranked by PFFR

Name Team PFF Grade PFFR
LeSean McCoy PHI 27.5 11.4181818181818
Andre Ellington ARZ 8.2 14.390243902439
Donald Brown IND 5.4 18.8888888888889
LeGarrette Blount NE 7.8 19.6153846153846
Marshawn Lynch SEA 15.1 19.9337748344371
Jamaal Charles KC 12.7 20.4724409448819
Arian Foster HST 5.9 20.5084745762712
Adrian L. Peterson MIN 12.9 21.6279069767442
Danny Woodhead SD 4.9 21.6326530612245
DeMarco Murray DAL 10 21.7
Daniel Thomas MIA 4.9 22.2448979591837
Montee Ball DEN 4.7 25.531914893617
Eddie Lacy GB 10.9 26.0550458715596
Alfred Morris WAS 9.7 28.4536082474227
Pierre Thomas NO 4.9 30

Ellington, Brown, Foster, Woodhead, Blount all show well in on a rate basis.

3-4 Defensive Ends - Pass Rush

In another tidbit of interest to Jet fans, the statistical or graded answer to Who is the best pass rushing 3-4 Defensive end we see interesting variables between PFF grades, PFFR ratio, and the PRP stat used by ProFootballFocus to quantify pass rush productivity. PRP counter sacks, hurries and pressures, with hurries and pressures downgraded to .75, and it is a rate stat. This is one of the best advance stats out there in my opinion. Here is what the PRP rankings look like:

Deprp_zpscb461729_medium

What we have is a nice little rate graph, which shows, as we all know, that J.J. Watt is a beast, leading all other 3-4 DEs in a significant but not absurd way. For instance he was a little less than twice as effective in pressuring the QB than the beloved Wilkerson. But what happens when we look at PFF grades? See below:

Depffgrade_zps66ce1552_medium

Suddenly J.J. Watt is 8 1/2 times (!) more effective as a pass rusher than Wilkerson. Wow, he must be good.

If we adjust the PFF grade rankings, using the same top DEs, what happens to the list? Below are those players ranked by PFFR ratio.

Name PFFR PFF Rush Grade
J.J. Watt 9.57486136783734 54.1
Cameron Jordan 18.5512367491166 28.3
Vinny Curry 20.2803738317757 10.7
Antonio D. Smith 21.9148936170213 18.8
Kyle D. Williams 26 20.5
Calais Campbell 27.6576576576577 22.2
Mike Daniels 28.2203389830508 11.8
Justin Smith 35.8139534883721 12.9
Corey Liuget 69.3650793650794 6.3
Muhammad Wilkerson 94.7619047619048 6.3
Brett Keisel 105 2.8
Fletcher Cox 106.346153846154 5.2
Cameron Heyward 112.888888888889 4.5
Arthur Jones 125.263157894737 1.9

A player like Vinny Curry really jumps up in the grade list. Watt generates a +1.0 grade about every 10 times he rushes the passer, almost twice the rate of 2nd place Cameron Wake. Boy those Houston graders love hitting the +1 button on the keyboard. But look what happens to Wilkerson. He went from being almost half as effective (PRP), to 1/8 as effective (PFF rush grade), to now 1/10th as effective as Watt (PFFR ratio). As PFF graders see it, it takes Muhammad nearly 100 pass rushes to produce the same effect on the game as Watt does in 10.

In this case PFFR reveals maybe some of the bigger problems with the grading system, the way that things really can get inflated (in perhaps both directions), but it also (possibly) reveals hidden graded pass rushing gems like Vinny Curry who did not have enough rushes to quality for the first PRP graph, he would have been 2nd on that list with a PRP of 11.6 to Watt's 12.8.

Concluding Discussion

Above are just some examples of how taking rates of production into account changes rankings. Of course high-snap players have a kind of unspoken value to the team, and generally are better players, but PFF grades are supposed to be about performance quality, not so much performance volume. It can be argued that looking at rates of positive grade production is a little like rates stats like Yards Per Carry or even PRP. There are minimum qualifiers, but rate stats allow us to compare quality across variables like playing time which may be affected by roster depth, scheme or injury.


Of course people aren't going to start calculating new grade rankings, but it is suggested that if these grade numbers are going to continue to grow in popularity - something I kind of dread because of how subjective and distortive they are - if they are going to be used in player to player comparisons, which seems to be the trend, we should also be looking at the snap, target and pass rush numbers that occurred to generate these grade values. It should be part of the conversation.

Thanks to Buzzy for thinking about this and making a point about it.

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