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Chasing the Grail, Part Two

Here are all the charts and research that didn't fit into the other post.  First, I'll start with the distributions of defensive seasons from 2002-2009 (as measured by UZR, minimum of 500 innings played) by position and then I'll provide some numbers on means and standard deviations.  Let's start at the beginning of the defensive spectrum and work our way towards the most difficult positions:

 

Mean

Median

Std. Dev.

1B

0.11

0.45

5.23

LF

-0.78

-1.25

8.79

RF

0.08

0.65

9.77

3B

1.00

0.40

8.57

CF

0.90

1.30

9.92

2B

0.36

0.10

7.64

SS

0.77

0.90

7.98

C

?

?

?

Overall=

0.36

0.5

8.385781

If I squint really hard, I can almost see my theorized "trend" from 1B to SS, but I think that's just wishful thinking on my part.  There is a small increase in the mean UZR per position as you climb the defensive spectrum, but it's so small I think it's pretty negligible and can be discounted as random noise.  Maybe someone with more of a background in statistics will be able to determine if there's a statistically significant trend in the data here, but just from the eyeball test, it doesn't seem to pass.

That said, if there is no noticeable trend, then it follows that all positions follow the normal curve.  Some deviate more than others, but for the most part the positions do hold very true to the overall distribution of defensive ability.  And if that's the case, we can assume that catchers most likely fall within the same curve and will have defensive seasons that follow the curve.  So through this method, here's the breakdown of catcher UZR scores (or for UZR breakdown at any position, for that matter):

This is just a general idea of what to expect in the long run, so the distribution on a season-by-season basis could vary slightly from this.  Now, let's look at all the catchers that logged more than 500 innings last year behind the dish, as ranked by Tom Tango's Fan Scouting Report.  Players are broken up by their distance from the mean, with 3.09 being the mean and .487 being the standard deviation:

The percentages work out very close to what we'd expect from the normal distribution of defensive ability, with 72.5% of catchers falling within one standard deviation of the mean (68% expected), 25% falling between one and two standard deviations from the mean (27% expected), and 2.5% falling between two and three standard deviations from the mean (4% expected).  Now all that's left to do is to turn the Fan Scouting Report into UZR by using the standard deviations listed above.  I tried to make it as accurate as possible, weighing where players were ranked within their standard deviations as well.  Here's the final result:

Of course this is merely an estimate and shouldn't be taken as gospel, but if nothing else I had fun putting it together.  Enjoy!

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Isn't UZR compared to the average player at each position anyway?

So, it would make sense that each position is just about centered on the normal curve, and I bet as we get more defensive data each position will look more and more like the normal. To be honest, I really like this, the only problem is that all the data is coming from one source (fan scouting report), so it’s hard to know how reliable the source is. I feel like if a bunch of different scouting reports are available to mash together this would actually be a legitimate tool to evaluate catchers. At the same time though, the question still remains if an average catcher is worth more than an average shortstop. Very cool though

by Matt Slowinski on Mar 10, 2010 4:08 PM EST reply actions  

Yeah, the trick seems to be...

1. What’s the standard deviation for catcher UZR? Is it different than that at other positions? So far research seems to think it’s half that of the other positions, in which case you’d just divide the UZR totals above by two.

and

2. What’s the most accurate scouting/fan projection we can get for defensive ability? I’d like to look at how well the Fan Scouting Report for the other positions lines up with UZR, which could then give us an idea of how accurate it would be to apply to catcher.

I love Casey Fossum. Now try and take me seriously.

by Steve Slowinski on Mar 10, 2010 6:13 PM EST up reply actions  

I think I agree

1. While the catcher is involved in every play in some way (assuming they call pitches), the average catcher does more things than the average fielder, but at the same time, they have an effect on balls put in play far less often. For that reason, I would tend to think that the std dev. would be lower, since for each year there should be less of an opportunity for each catcher to distance itself from the pack (in either direction). Then there’s still the question of whether or not framing, pitch calling, blocking the plate, etc should factor in at all, of course

2. That would definitely be the next step, because then you could probably extrapolate some likely error bars for the catcher numbers you come up with, to give a more likely range. Ultimately, catcher defensive stats are probably going to be less precise than the normal fielding positions, IMO

by Matt Slowinski on Mar 11, 2010 12:05 AM EST reply actions  

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