17 December 2013

The Degradation of Wieters' Pitch Framing: 2010 - 2013

One of the more difficult positions to assess defense in a quantitative way has been catching.  What makes it difficult is that a catcher has far more choices to make that mingle with his talent level.  That is much different from, say, a center fielder who for the most part is simply reacting to a batted ball, making a catch, and, perhaps, deciding and carrying out a throw.  For a catcher, you have the throwing game, blocking the plate, preventing passed balls, calling the game, and pitch framing.  On the last point, considerable progress has been made by using Pitch f/x, which is available in every MLB stadium and provides a myriad of quantitative descriptions for every pitch thrown in baseball.  One can use this system to identify the exact point where a ball passed over the plate and surmise whether it was really a strike or a ball.  What we have found is that catchers tend to repeat their scores year in and year out.  A repeated number points toward an actual skill.

Lou and I have been toying around with these numbers.  So have others.  The numbers I am using for this post are from statcorner.com.  Below is a table of catcher who from 2010 to 2013 caught at least 5,000 pitches in each season.  The value is expected runs per 10,000 pitches (which is basically how many pitches a catcher catches if he played about 145 games).

2010 2011 2012 2013
Brian McCann 31.4 33.2 27.3 15.3
Jonathan Lucroy 39.6 44.0 35.7 32.9
Yadier Molina 20.4 14.2 18.7 22.2
Russell Martin 15.3 27.2 26.4 20.4
Carlos Ruiz 10.1 -12.4 7.2 -9.1
Miguel Montero 13.4 15.2 6.5 -1.7
Matt Wieters 6.9 3.1 -4.5 -8.7
A.J. Pierzynski 2.2 11.8 -6.9 -13.7
Kurt Suzuki -6.0 -5.6 -6.5 -16.4
John Buck -23.3 -16.8 -0.9 -28.6

As you can see, the rates can vary a bit, but they are actually rather remarkably consistent as shown in this graph where one year's value is compared to the next year's value.

An excellent number one year tends to result in an excellent number the following year.  One might be concerned about how the trend is well defined on the runs saved end of the spectrum, but not very filled on the runs given side.  This is most likely an issue with survivorship in the population.  In other words, if you are bad at pitch handling then you will probably not be catching a lot over several years of play.

How does Matt Wieters fit into things?

In general, we don't expect much change based on aging curves for pitch handling based on a previous study.  Wieters is showing a gradual erosion of runs saved and his performance, according to this metric, was subpar the last two seasons when compared to the league average.  He certainly excels in other parts of his game, such as throwing runners out, preventing passed balls, and blocking the plate.  Those other skills have earned him a couple Gold Gloves and developed a strong defensive reputation, something no one thought possible when he was drafted.  However, it appears his defensive profile is not perfect and its imperfection is found in a metric that is commonly not included in nearly all quantitative ways to measure defense for a catcher.  In other words, he likely is being given credit for all of the things he does well, but is ignored over what he probably is average or below average at.

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