Comments on Defensive Runs

I started doing this DR stuff after the 1992 DAs came out to see if I could determine whether Jeff Blauser was more valuable than Rafael Belliard. There are a variety of methods out there for telling us how valuable a player's offensive performance was. It is also common stathead wisdom that good offense can make up for bad defense, and that those good glove/no hit players that managers like really are valued more than they should be.

But I have never really seen any stats attempting to prove this, probably because without DA-style numbers its hard to get a handle on how valuable someone's defense is. Once the data became available, though, it became possible to check our hypotheses about defensive value.

So, given the basic validity of Sherri Nichols's DA method, we ought to try and translate those numbers into something directly comparable in the offensive realm. I chose to model my DR numbers after the two endproducts of David Tate's MLV analysis: MR/G (number of runs per game contributed offensively to an average team) and TMR (total number of runs contributed by a player to an average team, for a whole season). I find the idea of breaking down a player's contribution into runs an aesthetically pleasing way of describing his value. We all understand what runs are, and we know that ~10 runs adds a win in the standings, which ultimately is what we are after.

Okay, with all that in mind, here are some points that need to be made about DR:

Finally, here is Blauser vs. Belliard '92, using MR/G from Dave Tate's final MLV post for that year (drumroll):

			 MR/G	 DR/G 	"Total Value"
	Blauser:	+.141	+.081 	  +.060 runs per game
	Belliard:	-.302	-.058	  -.244 runs per game
(Total value = MR/G - DR/G, since negative DR/Gs mean good fielding).

Not even close - Blauser's bat beats Belliard's glove, hands down.