From: steph@cs.uiuc.edu (Dale Stephenson)
Subject: Defense (was Re: AL Rookie of Year Award?)
Organization: University of Illinois, Dept. of Comp. Sci., Urbana, IL
Date: Wed, 30 Sep 1992 23:06:23 GMT

In <1992Sep30.165229.17325@panix.com> spira@panix.com (Greg "Sarcasm Is A Way Of Life" Spira) writes:

>In <1992Sep30.052108.4215@Princeton.EDU> niepornt@phoenix.Princeton.EDU (David Marc Nieporent) writes:

>>True, but on the other hand, you could argue the exact opposite.
>>Because a shortstop is more important than a centerfielder, a poor
>>shortstop hurts the team *more* than a poor centerfielder.

>In terms of value relative to an average player at that position, of
>course.  But I don't really believe comparing players to average is 
>the right way to measure value - I don't really believe that half of
>major leaguers have "negative" value.

I agree that average is the wrong thing to compare to.  Nor do I believe
that all players have positive defensive value.

>>You seem to be arguing that: 
>>	defensive value = (defensive ability) * (positional value)
>>There's nothing wrong with that.  But if that defensive ability is
>>negative, then the defensive value is negative, too.

>Yes, but I don't consider defensive ability to be negative unless the
>player is below replacement value.  And I think the positional value
>number is quite high.

So what we really need here (besides accurate defensive numbers) is an
estimate of "replacement level" defense at each position.  Any way this
can be calculated?  My dream would be to figure out how many extra hits
a player will give up/take away on defense at a given position.  Then we
could compare players at different positions straight up.

>>>To move to an easier example, would you agree that the worst shortstop
>>>is worth more than the best first baseman? Or a DH?

>>No.  Just as a player can have a negative value on offense, they can
>>also have a negative value on defense.  If your scenario *were* true,
>>then no team would ever put a light-hitting middle infielder on the team.
>>Because ANYONE could be "the worst shortstop," including Frank Thomas.

>But I'm talking about real shortstops.  And the fact is that real shortstops
>- even bad ones - can get away with worse offensive numbers than the best
>defensive first baseman and the shortstops in question would keep their jobs
>while the first baseman, if they had as bad numbers as the shortstop, would
>lose his job. ( A terribly written sentence, but I think the point is clear).
>For this to be true, the shortstop has to have more defensive value than the
>first baseman.

Even bad ones?  If Blauser hit like Belliard, he wouldn't keep his job very
long.  The reason bad-hitting shortstops keep their jobs is because their
replacements also tend to be bad hitters.

Blauser is valuable offensively because his replacement would not hit as well.
If a replacement-level shortstop hit 300/400/500, Blauser would be an offensive
drag on the team.  Why should Blauser be considered valuable defensively, when
anyone who replaces him is likely to field better?
--
Dale J. Stephenson |*| (steph@cs.uiuc.edu) |*| Baseball fanatic

  "It is considered good to look wise, especially when not 
   overburdened with information" -- J. Golden Kimball
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