Old Mother Hubbard
Went to the cupboard,
To give the poor dog a bone:
When she came there,
The cupboard was full of talented young football players,
which was pretty awesome.
Yes, it’s time once again for The Lions in Winter’s annual roster analysis/team needs thing, Old Mother Hubbard. Last season’s edition added Pro Football Focus grades and statistics, plotting them on radar charts for easy understanding. This was well received.
I highly value PFF data, they do fantastic work that nobody else is doing. As I said, if I had the time to grade out every Lion on every snap of every game for these breakdowns I would—but PFF already did, so I stand on their shoulders.
However, I don’t think PFF data is the only valuable way of describing a player or season. I’m a big fan of the work Brian Burke does at Advanced NFL Stats, and I’m going to be including (at least) his Win Probability Added stat, WPA. Burke explains WPA here:
Stats are tools, and each tool has its own purpose. WPA is what I call a narrative stat. Its purpose is not to be predictive of future play or to measure the true ability of a player or team. It simply measures the impact of each play toward winning and losing.
WPA has a number of applications. For starters, we can tell which plays were truly critical in each game. From a fan’s perspective, we can call a play the ‘play of the week’ or the ‘play of the year.’ And although we still can't separate an individual player's performance from that of his teammates', we add up the total WPA for plays in which individual players took part. This can help us see who really made the difference when it matters most. It can help tell us who is, or at least appears to be, “clutch.” It can also help inform us who really deserves the player of the week award, the selection to the Pro Bowl, or even induction into the Hall of Fame.
There are two main weaknesses with PFF grades—or perhaps I should say, two main characteristics you need to keep in mind when evaluating players with them. First is a strong pull towards the mean. Since an unremarkable play—a typically decent effort—gets graded as a zero, the fewer snaps a player has the more “average” he tends to look in his grades. PFF acknowledges this with a default minimum of 25% of available snaps, but it limits their utility in describing role players and backups.
The other factor is what I call a “consistency bias.” PFF’s grading system loves players who make consistently positive down-to-down impact, and tends to pooh-pooh “home run hitters” who make a couple big plays per outing. WPA works in the opposite way: it loves players that makes plays that win games. Between the PFF data and WPA, we should get a very complete picture of how strong the Lions’ roster is, relative to itself and relative to the rest of the NFL.
Number crunching is happening now; OMH's start going up by the end of the week.