So, those of you that have had more than a beer or two with me lately know that for the last year or so I have become intrigued with the so called sabremetrics (or statistical) approach to looking at baseball performances. My interest in this topic has been fired by the Seattle Mariners blog community. It turns out that the two biggest blogs covering the Mariners both take a decidedly statistical approach to analyzing baseball performances. From there I started thinking about and looking into what work has been done in this realm for other sports. This post is a discussion of the new thinking as it applies to the Portland Trailblazers.
Before discussing where the Blazers are and where they could be going, it would be helpful to give a basic description of what new statistics I am talking about and why things like points per game should become obsolete in the near future much as ERA has.
Some of the my favorite work to date has been done looking at offensive and defensive efficiency. The concept is this: Basic statistics measure how many points a team scores and how many points a team gives up. But, these numbers doesn't exist in a vacuum, and teams that score fewer points don't necessarily have worse offenses. If a team is more deliberate in it's offense, if it uses more of the shot clock each trip down the floor, that team will have fewer overall possessions then a team that shots quickly (like the Suns of the last couple of years). Even a team that is efficient in terms of how it uses it's possessions may score fewer points in a game than a less efficient, but faster team.
Since a game is of a defined length (48 minutes in the NBA) it isn't too difficult to calculate the number of possessions per game a team gets (See here: http://www.basketball-reference.com/about/glossary.html for the formula)* Once we know how many possessions a team has in an average game we can look at how many points per possession a team generates. Although this could be a useful measure, most sites extrapolate out to points scored per 100 possessions to compare across teams. This is useful not just to see how efficient an offense is, but it can also be used as a measure of team defense. Looking at offensive and defensive efficiency will give you a basic measure of a teams health.
Although there are other advanced statistics that bear discussion, today I am going to talk about The Four Factors. This is a concept advanced by Dean Oliver in his book Basketball on Paper. Now, this discussion should come with the caveat that I haven't read that book yet. As such, this discussion will be somewhat cursory. The idea is that a basketball game can be broken down into (shocked face) Four Factors:
Shooting
Rebounding
Ball handling
Getting to the free throw line.
This may sound a little simplistic, but it should be noted his work was good enough to get him a job with the Seattle Supersonics and the Denver Nuggets as a full time statistical analyst. Since I am starting to run out of time, tonight I will cover the basics of the four factors and the simple, but more useful statistic.
1) Shooting
When talking about shooting, normal FG% isn't enough. Specifically it fails to account for the added importance of a 3 point field goal. Since a three is worth 50% more than a two, we need to use a waited percentage. This number is generally referred to as “effective field goal percentage” or eFG%. Simply put eFG = (fgm + .5*3fgm)/fga.
2) Rebounding
Once again per game stats are insufficient to measure how well a team does. Per game stats don't account for the number of rebounds that are available in a given game. The better measure is offensive and defensive rebounding percentage. These numbers are fairly self explanatory.
OReb% = OReb / (OReb + Opp DReb)
DReb% = DReb / (DReb + Opp OReb)
3) Ball Handling
Rather then just looking at pure turnovers per game, we can use a possession based statistic: Turnover % = Turnovers / Possession.
4) Free Throws
This one is a little more strange. Although we could just look at FTA or FTM, its always better to take into account the pace of the team you are talking about. Most researchers look at FTM/FGA and dub this “free throw rate”.
None of these stats is the be all end all, and all statistics can be effected by factors that aren't necessarily what we are trying to measure. Alright, it is getting late tonight. Sometime tomorrow or later this week I will drop a post discussing what these numbers say about Portland and where they need to improve.
*Basketball reference is an awesome site. If you like basketball and/or statistics, it is a site you can lose a lot of time at. Their formula is quite good, but also a bit complex. If you need a short version FGA + TO + ~.5 FTA – ORB will get you close, but it isn't particularly exact.
3 comments:
Hey Beau. I suppose after watching the Finals I should be all ready to look at more basketball stuff, but really I'm just twiddling my thumbs until September rolls around and football season starts. For something similar to basketball reference, only for football, try Football Outsiders. The final product they talk about lumps lots of things together, but they also have lots of nice tables that you can look at to see specific information. It takes a while to get used to, but at least they go beyond the usual base measures of points and yards. In the last two years they've taken on a "game charting" project where they record what happens on every snap of every game, and have been doing some really cool analysis with that. I don't think (and they don't really, either) that we'll ever get to the point where you can tell how good an individual player is independent of the other 10 players around him (not to mention the 11 guys across from him!), but they're trying to tease that sort of individual information out.
As an aside to this football aside from your basketball post, they've also brought someone in who's trying to do some more "advanced statistics" for college football, but I think that's just crazy. The game at that level just isn't nearly as uniform and you need to have some kind of baseline to work with for this kind of work. It may seem weird to try and compare the offenses of the Patriots to the 49ers last year given how different they were (passing vs. running), playing in different conferences, and so on. But that makes a hell of a lot more sense when you think about trying to compare Hawaii vs. Northwestern.
Hm, I didn't know people were doing this with basketball. I assume you read Moneyball, right? Anyway, I can't speak for anyone else, but I'm looking forward to part II, especially if there's some draft day/point guard trade pointless conjecture.
Eric, I should probably be mad at you for how much more time I am now going to spend swimming in numbers, acronyms and advanced statistics. Or maybe it is Sam that should be mad to you...
Rip, I am glad you enjoyed it. I will try to work up something as far as actual moves/changes that I would like to see Portland do this off-season, but it didn't make it into the second post on this one.
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