17th?! A discussion with PFF’s Eric Eager
Oh jeez. Yeah I can see where people can get irritated here.
Yesterday, for those who follow Vikings twitter, Pro Football Focus posted one of their outstanding graphics, but this time it was a complete head scratcher. PFF had ranked the Vikings defense in 2016 as 17th overall. “Whoa!”
This started off a series of conversations that ended up being a interview with Eric Eager of PFF. First a little bit about Eric. When most people think of Pro Football Focus, they think these stats are the dream children of math loving, spreadsheet crunching, algorithm making nerds that are trying to quantify football. In this case, that is is true, but there is much, much more. Did you know that most of the people working on football statistics at PFF, actually come from a football background? That is true, and is the case for Eric too. Besides being a professor in enemy territory at the University of Wisconsin La Crosse, Eric possesses a PhD in applied mathematics and mathematical biology. He was also was a starting tight end for Moorhead State University here in Minnesota during undergrad school. Best yet, he grew up being a Vikings fan.
PFF posted a graphic of NFC North defense rankings and had the Vikings ranked as 17th. The NFL had the Vikes ranked as 3rd overall, #3 against the pass YPG and #20 against the run YPG. Fans knowing that those [YPG] stats can be simplistic and that they don’t correlate to a lot of what PFF does, there were still a lot of fans that were like, “what?!”.
Fans were wondering what all goes into a defensive team ranking at PFF? Eric started out by saying, “It starts with grading each player on each play each game. Then some math to normalize, and then figuring out how much each action is worth.” So it is a player focused process and other stats are team based, an apples and oranges type comparison. We know that Barr had bad games and injuries, Smith’s play declined due to injury, MacKenzie seemed lost at times when he was forced to play, etc. Those individual grades can bring down the unit even though as a defense, they were quite effective.
Sam Monson, the PFF Lead Analyst chimed in too, “We're grading every player individually not just looking at results of the play which can mislead at times.” He even has the Vikings defense ranked higher at #11 on his end of season rankings. PFF explains on his rankings that the “overall cumulative grades as a starting point and makes necessary subjective adjustments to account for things that aren’t captured in the grading, such as injuries.”
The win-loss record in 2016 was by definition, was average, even though we viewed the defense as a top 5 D. Most fans blamed the failings on the offensive side of the ball, from horrid line play, Sam Bradford coming in at the last second prior to the season, Norv Turner quitting, and the myriad of injuries, etc.. Other than the defense running out of gas late in the season, they looked a lot better than virtually all of the defenses in the league. In the first 5 games they were elite. It was that the offense didn’t come close to being productive enough. That #17 ranks looks way low.
We wonder by having the evaluations being player based, has PFF overlooked or considered overall team effectiveness? If you have some great players but average team results ranking higher than a team with good players but with better team results?
“What's an example of that? I've found that rankings using our grades generally predict subsequent seasons better than W/L results” Eric asked.
An approximate sum of each single player may not take into account of how they play together, i.e. “chemistry”. Say you rank D team performance on the same type scale, (+) scores for effective stops, (-) scores for yards or position given up, etc, and the opposite for the O, then see how those cumulative scores compare to the approximate sum of the individuals. It might point to other desirable factors in a player like their communication skills with teammates, maybe leadership indicators, their team versus individual focused plays like when a defender takes a position to contain and turn a play in for other defenders to make the stop versus trying to make the Sports Center type hit. This might be extremely valuable and an added feature fans and teams might very much want to see.
Discussing that 17th ranking, it does not bode well for the 2017 Vikings defense. “They're going to be better than 17th next year, and their grades were more of a reflection on what happened in 2016 (especially at the end) than how good the players on their team actually are.” Eric empathically responded.
PFF has always been a good starting point for conversation. Hopefully now that we know that their analytics are player focused, a fan can use that to their advantage when evaluating a team. So if the Minnesota Vikings rank #17 in defense per PFF, meaning that’s the accumulation of each player’s scores, and yet ranks better in other forms of statistics that may indicate team play such as the NFL’s 3rd overall ranking, or for added context, Pro Football Reference’s data that had them ranked #6 overall on defense last year, we can conclude that the Vikings got better play than the sum of all their parts. We know Mike Zimmer doesn’t particularly like Pro Football Focus statistics publicly, but he might point to this as an indicator on how he and his staff does with the players they have. That is a very good thing and forecasts well for the Vikings.
I wish to extend a personal and Daily Norseman thank you to Eric Eager for his time and insights as well as the contribution of Sam Monson. Their willingness to share this invaluable perspective can add to a fan’s experience of the game. Also, I wish to give a shout out to Luke Braun over at Purple PTSD for the initial discussions on this topic and connecting me with Eric. Thanks again gentlemen.