Friday, August 31, 2012

Fun With Lists: Comparing Stats and the Eye Test


I've been following #NBArank, the ranking of 500 NBA players by a panel of experts including ESPN broadcasters, writers and TrueHoop network contributors. #NBArank always creates a bit of controversy, which helps an addict make it through another slow August news day. For example, today's rankings of players 201-220 included this tweet by Sammie J.:
Omri Casspi (208) somehow ranks way higher than Alonzo Gee even though Gee (271) took his starting spot last season.
This may be an example of bias resulting from a player who gets a good bit of press (Casspi) being compared to a player who doesn't (Gee). Nevertheless, this panel includes a ton of basketball junkies with league pass. Think of #NBArank as a sort of eye test. Although ESPN's John Hollinger is among the panelists, few of them likely go into near the depth of statistical analysis that Hollinger employs.

That got me curious to see how #NBArank compared to Player Efficiency Rating, the forumula developed by Hollinger to compare players based on raw statistics. For my sample, I was specifically curious to see how incoming and outgoing Hawks players ranked in both PER and #NBArank.

As of this writing, ESPN.com has listed players 201-500 for this year. The Hawks lost Joe Johnson, Marvin Williams and Kirk Hinrich among players that will rank in this year's top 200. Among incoming players in that category, the Hawks gained Devin Harris, Lou Williams, Kyle Korver and Anthony Morrow. The following shows the #NBArank (where available) and PER rank for each incoming and outgoing Hawks player.

Incoming players       Rank PER

Lou Williams            -         37
Devin Harris  -        104
Kyle Kover                -        188
Anthony Morrow        -        209
Johan Petro              397    284
DeShawn Stevenson  319    351
Jordan Williams        457    154

Outgoing players

Joe Johnson  -      56
Marvin Williams          -      108
Kirk Hinrich               -      302
Tracy McGrady            240  180
Willie Green              308  177
Jannero Pargo          382  180
Vlad Radmanovic        329  246
Erick Dampier           420  440*
Jason Collins           391  457*

* PER ranks 352 qualified players who averaged at least 6.09 MPG. Dampier and Collins did not qualify, so their rank is among all 478 players who appeared in at least one game.

The first thing that jumped out at me after compiling these numbers was that PER seems to favor defensively-challenged volume shooters. Willie Green and Jannero Pargo stack up relatively well in PER compared to their #NBArank. I personally laid much of the blame for the Hawks' loss to the Celtics in the first round of the playoffs on Larry Drew's over-reliance on Pargo and Green. The two were -26 and -40 in +/- for the series, respectively, by far the worst on the team. ESPN's panelists seem to agree that Pargo and Green are not as valuable as their PER might suggest.

Another discrepancy is Johan Petro, who falls behind Jason Collins in #NBArank but sports a superior PER. But the biggest discrepancy is Jordan Williams, who falls almost to the bottom of #NBArank at 457 but ranks in the top half of qualified players in PER. Williams might be another player like Gee who suffers from a lack of publicity. Or he might be a player with a PER inflated by stats amassed on a lottery team. Williams last year was statistically similar to Ivan Johnson, who was named Eastern Conference Rookie of the Month for April. 

While I certainly hope that Williams proves to be an underrated commodity, I feel fairly confident that Johnson will prove to be the better player. Thus why I'm on record stating the importance of the Hawks retaining Johnson. I also feel that Drew would do well to bury the hatchet with Tracy McGrady and welcome him back to the roster. T-Mac looked good in the playoffs and is the most highly-regarded member of last year's roster that remains a free agent. 

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