Posted by: M | February 21, 2011

Overrated Statistic of the Day: Blocked Shots

Statistics are interwoven in the very fabric of sport.  They’re used to assess greatness and futility.  Used to gamble and used to develop game plans.  They may even be part of the reason young boys are better at math than young girls.  (But probably not).

Some, like Oakland A’s General Manager Billy Beane and Mets General Manager Sandy Alderson live and die by the statistic. Others, like my Grandpa don’t really care for the statistic.  However, regardless of your point of view of the role that statistics should play in sports, there can be no denying that some statistics have value and others do not.

There can also be no argument that some statistics are widely held to have a great deal of value.  And many do.  But some statistics that tend to be widely agreed upon barometers for success may not be as important as they have been made to be.  A few that come to mind: wins and fielding percentage in baseball, penalty minutes in hockey, passing yards in football, etc.  Today we discuss one statistic that I find to be glaringly overrated:  the blocked shot in basketball.

Statisticians have begun to question the value of a blocked shot.  I have also, but with a bit of a caveat.  Do I think blocks are valuable? Yes.  Do I think blocked shots can be indicative of a particular aspect of an NBA player’s game?  Yes.  But do I think blocks, as the statistic is presently constituted, is a good indicator of defensive ability? Absolutely not.

Let’s start with the obvious.  A block is not a steal.  A block is not necessarily a turnover.  More often than not, blocks – particularly the ones that make SportsCenter and the evening news – are swatted out of bounds by the defender.  This is followed by some type of animalistic yell by said defender, be it Lebron, Dwight Howard, or even my beloved Amare.  Following said yell, the offense inbounds the ball and the possession continues.  Maybe the offense gets an even higher percentage shot than the one that was blocked.  Put another way, blocks may be violent and fun, but in reality, they don’t necessarily translate into fewer baskets scored – or at least as many fewer baskets scored as one would believe.

Seemingly gone from the sport is the Bill Russell-esque blocked shot that would lead to a fast-break the other way.  University of Chicago Professor John Huizinga refers to these types of blocks, quite appropriately, as “Russells.”  According to his research, only an average of one player per year accumulates more than twenty “Russells.”

Another issue: there is only one category of blocked shot as currently constituted.  But is blocking a jump shot really as valuable as blocking a layup? Surely not.  A study performed by MIT statisticians found that a jump shot has an expected point value of 1.04.  A lay up, on the other hand,  has an expected point value of 1.54.  You do the math.

Yet another issue the statistic fails to take into account is the situation in which the block takes place.  Surely when Lebron (that bastard) chases down an opponent on a fast break, that block is more valuable than when a player blocks another player’s shot taken from the half court offense.

At the end of the day, a better statistic is what Huizinga refers to as “block value.” To determine block value, he used the formula Points Saved + Points Created where:

  • Points Saved is defined as the effect of a block on the opponents expected points during the current possession, and
  • Points Created equals the effect of a block on the defender’s own team’s expected points during the ensuing possession.

Using this formula, Mr. Huizinga pointed out who, by his estimation, was the most productive blocker in the NBA and who was the least productive.  The least productive – Dwight Howard.  Howard only saved .53 points per blocked shot.

Can you guess who the most productive shot blocker in his study was?  Of course you can.  Who else would it be?  The Big Fundamental himself, Tim Duncan.  Duncan saved an average of 1.12 points per blocked shot.

So what does this all mean?  Who knows.  All I know is that blocked shots do not equal defensive prowess.  Just ask Amare Stoudemire (who, again, I love).  He is averaging 2.2 blocks per game this season.  He’s third in the league with 117 total.  Amare is NOT a good defender.  We all know this.  Blocks are fun.  Blocks can be momentum changing.  Blocks can even be game changing.  But until defenders start learning how to “Russell” again, blocks will not be a reliable indicator of defensive ability.

I encourage you to read Huizinga’s full report.  It is very interesting stuff.


Responses

  1. Amen

  2. I tried to follow to your rss provider, but there was a error appending it to google right ascension


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