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Monday, February 23, 2009

The Proper Application of Basketball Statistical Analysis

Although I wrote a post titled Economics is Not a Science, Nor is Basketball Statistical Analysis, I certainly support any and all efforts to make basketball statistical analysis more precise and scientific. As I wrote in that article, "No one should misinterpret what I am saying to mean that I am some kind of Luddite who is against using basketball statistics; what I am against is the misuse of basketball statistics, just like I am against the misuse of media platforms by people who spout hype and biased commentary as opposed to communicating information in a fact based, objective manner."

Daryl Morey, the General Manager of the Houston Rockets, uses basketball statistical analysis as one tool to evaluate players but, as Michael Lewis explained in a recent New York Times article, Morey is fully aware that numbers only tell part of the story and that to completely understand what happens in a basketball game you have to watch the sport with understanding.

Here is an examination of what Lewis' piece tells us about basketball statistical analysis, and what Lewis' piece says about why Shane Battier defends Kobe Bryant as well as any other player in the NBA:

A recent New York Times article by Michael Lewis provides an intelligent, in-depth discussion of how basketball statistical analysis can be properly applied to help executives and coaches make personnel and strategic decisions that will increase their team's chances to win. Lewis focuses on the stories of two people: Houston Rockets General Manager Daryl Morey and one of Morey's prize acquisitions, forward Shane Battier.

Battier won the 2001 NCAA Player of the Year award but he is nevertheless -- in Morey's words --"at best a marginal NBA athlete." Morey notes that virtually the only way Battier can score is by making spot-up jumpers right after receiving a pass.

Morey explains, "That's the telltale sign of someone who can't ramp up his offense. Because you can guard that shot with one player. And until you can't guard someone with one player, you really haven't created an offensive situation. Shane can't create an offensive situation. He needs to be open." Morey concludes, "He can't dribble, he's slow and hasn't got much body control."

This frank assessment of Battier's physical limitations did not prevent Morey from discerning that Battier can be a valuable member of a playoff caliber NBA team. What did Morey see in Battier that many other observers -- including Houston owner Leslie Alexander, who initially was very skeptical about trading for Battier -- did not? Here is Lewis' explanation:

Battier's game is a weird combination of obvious weaknesses and nearly invisible strengths. When he is on the court, his teammates get better, often a lot better, and his opponents get worse -- often a lot worse. He may not grab huge numbers of rebounds, but he has an uncanny ability to improve his teammates' rebounding. He doesn't shoot much, but when he does, he takes only the most efficient shots. He also has a knack for getting the ball to teammates who are in a position to do the same, and he commits few turnovers. On defense, although he routinely guards the N.B.A.'s most prolific scorers, he significantly reduces their shooting percentages. At the same time he somehow improves the defensive efficiency of his teammates -- probably, Morey surmises, by helping them out in all sorts of subtle ways. "I call him Lego," Morey says. "When he's on the court, all the pieces start to fit together. And everything that leads to winning that you can get to through intellect instead of innate ability, Shane excels in. I'll bet he's in the hundredth percentile of every category."

Morey tells Lewis that in basketball there can be, as Lewis phrases it, "a tension ... between the interests of the team and the interests of the individual." This does not exist so much in baseball or football. "There is no way to selfishly get across home plate" is the analogy Morey uses; in contrast, Morey says that when he worked for the Celtics the team had a point guard who would not pass the ball to a particular player, something that would not necessarily negatively affect that point guard's statistics but definitely negatively affected the team.

A basketball player can amass good individual statistics but not really be helping the team overall; my favorite example of this phenomenon is Stephon Marbury, who has produced more 20 ppg/8 apg seasons (six) than anyone other than Oscar Robertson (10)--but Marbury has made every team he joined worse (and every team he has left has gotten better, including this year's Knicks after management banished Marbury). Morey points out that at contract time, assists are more valuable for a point guard than points scored, so point guards sometimes eschew their own easy scoring opportunities to make passes that they hope will turn into assists; although on the surface these plays may seem to be unselfish, each extra, unnecessary pass entailed a risk that slightly lowered the probability of the team scoring on that possession.

In contrast, Battier's value is that he is--as Lewis puts it--"the most abnormally unselfish basketball player" Morey has ever observed. Battier willingly sacrifices his personal statistics for the betterment of the team. Morey uses an adjusted plus/minus system as one analytical tool to evaluate players. Plus/minus simply records the point differential when a player is on the court versus when he is off the court, so the number can be "noisy" due to the impact that the other nine players have on the game but Morey uses certain methods that he will not disclose in order to get rid of a lot of the "noise." By Morey's reckoning, Battier's adjusted plus/minus ranks him among the very best players in the NBA.

Other numbers show that when players who are widely recognized as superstars are guarded by Battier they tend to have subpar games. Morey had to watch a lot of game film to figure out why this is the case and what he discovered is that Battier does a lot of subtle things to make the game more difficult for the player he is guarding. You can read the article to get all of the details about exactly how Battier does this but the important point is that Morey did not reach his conclusions about Battier merely by crunching some numbers; the numbers gave Morey some idea of what to look for but to complete his analysis he still needed to watch game film with understanding.

It cannot be emphasized strongly enough that Morey is not merely looking at spreadsheets and randomly assigning arcane values to certain combinations of numbers; statistics give him an indication of what to look for when he watches game film but he still has to watch game film to determine why players are putting up the numbers they do and to figure out what exactly those numbers mean.

In other words, Morey appears to understand the limits of a purely mathematical approach to the game and thus uses numbers to confirm what his eyes tell him--and vice versa. This is a completely different approach from the one taken by far too many stat gurus who are so enamored with their formulas that they dismiss the importance of actually watching games--perhaps because they are in fact not truly capable of watching basketball games with any real understanding of what is happening on the court.

A significant portion of Lewis' article delves deeply into the specific reasons that Battier is able to guard 2008 NBA MVP Kobe Bryant more effectively than just about anyone else in the league. Lewis notes that although Bryant "is better at pretty much everything than everyone else...there are places on the court, and starting points for his shot, that render him less likely to help his team."

Battier has an extraordinarily high basketball IQ, so the Rockets feed him scouting reports that are much more detailed than usual. Battier's genius as a defender is that during the game he is able to process all of this information and thus attempt to force Bryant to do things that he does relatively less well.

It is important to understand that neither Battier nor any other sole defender can truly shut down Bryant. As Sam Hinkie--Houston's Vice President of Basketball Operations and the head of the team's front office basketball analytics staff--says, "With most guys, Shane can kick them from their good zone to bad zone, but with Kobe you're just picking your poison. It's the epitome of, Which way do you want to die?"

Much of the latter portion of Lewis' article describes a Jan. 13 game that the Rockets lost to the Lakers, 105-100. Battier hounded Bryant into 13-32 field goal shooting but Bryant still scored 33 points and in the fourth quarter he had 13 points on 5-9 shooting, including a huge three-pointer with just 27 seconds left. The Rockets could be pleased that they forced Bryant into a below-average shooting night and that he had to make a low-percentage shot to clinch the game but the bottom line is that sometimes a player or a team can do everything by the numbers and still not be able to stop a great player. Of course, Morey believes that in the long run if the Rockets consistently play by the numbers--taking high-percentage shots and making low-risk plays while forcing opponents to do the opposite--then they will greatly increase their chances to win games, playoff series and, ultimately, a championship.

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posted by David Friedman @ 4:36 AM



At Thursday, February 26, 2009 2:13:00 AM, Blogger The Secret Asian Man said...

i also read the NY times and was very intrigued by morey's approach to evaluating a player's value. it's a shame that most fans will never go beyond box score stats.


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