Thursday, December 30, 2010

Catcher Defense - Part 4

Today, I'm going to finish my series on catcher defense.  The first three parts of the series can be found at the links below:

Catcher Defense - Part 1

Catcher Defense - Part 2

Catcher Defense - Part 3

In Part 3, I quantified catcher defense using the CatchRuns statistic.  This included components for stopping the running game, pitch blocking and avoiding throwing and fielding errors.  Sean Smith uses a similar method with the following differences:

1. He adjusts for handedness of pitchers.
2. He uses SB per inning and CS per inning instead of CS%
3. He uses different linear weights: -0.20 for SB, +0.47 for CS, -.275 for WP/PB.TE/FE.

Smith's results are included on Baseball-Reference under catcher runs above average (Rctch).

Another option is Fan Scouting Runs (FSR) developed by Tom Tango.  Hundreds of fans including some of you completed Tango's scouting report based on their observation of fielders.  Tango has now converted the results to runs.   

Because there is some disagreement between defensive measures, I have been computing averages across measures instead of relying on just one measure.  In this case, I'll take the weighted average (WtAvg) of CatchRuns Rctch and FSR.  I'd rather rely more on the two computed measures, so I'll give CatchRuns a weight of .4, Rctch .4 and FS .2.  I'll use Victor Martinez as an example:

CatchRuns -5
Rctch -6
FSR -8

WtAvg = 0.4 x CatchRuns + 0.4 x Rctch + 0.2 x FSR = 0.4 x -5 + 0.4 x -6 + 0.2 x -8 = -6

According to the weighted average, Martinez cost his team 6 runs compared to the average catcher.  The results for other catchers are show in Table 1 below.  Yadier Molina was the top catcher by any method and his weighted average was +16.  The bottom three catchers were Ryan Doumit, Bengie Molina and Jorge Posada at -10.

Table 1 - Weighted Average of Catching Stats, 2010

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