12-21-2008, 05:48 PM
Bz from what I have gathered, Dewan the fielding bible guy, grades every defensive play of every game. They grade every ball put in play and give it a value. From what I remember from the interview, there is a score for making an average play and a sliding scale for more points for making great plays. Not making a routine play deducts points. So, a shortstop making a play deep in the hole gets extra points, a shortstop not making that same play gets nothing taken away. A shortstop making a routine play gets some points added, a shortstop not making a routine play gets a lot of points deducted. Things that I found interesting in the interview is that the rankings for firstbaseman was very inacurate. No extra weight is added for double plays at all. Throwing arms for outfielders is really not factored in.
I am troubled by the fact that I really do not know who grades every game. There also seem to be some trends developing in the data they provide, like penalizing outfielders that play in large outfields and over valuing outfielders that play in small outfields. Trying to objectively grade 16 games a day for six months every year seems like an almost impossible task to me. With that being said, this is the best attempt at giving some actual value to defense that I have ever seen. The difference between the most and least amount of runs scored per year is around 200 per year, the difference between the most and least runs allowed per team is usually around 250 runs per year. As fans we spend so much time with the players offensive numbers and give almost no value to the defense they bring to the table this helps a bit. To me this a flawed system that has a tremendous amount of use full data, but everything must be taken with a grain of salt.
Here are the definitions from fangraphs.
<!--quoteo-->QUOTE <!--quotec-->Fielding
DG (defensive games): The number of outs made by an average fielder at his position given the exact distribution of balls in play for that player divided by the number of outs an average player at that position makes per game.
exO (expected outs): The number of outs plus reached base errors that would be made by an average fielder given the distribution of balls in play while that fielder was on the field.
RngR (range runs): The number of runs above or below average a fielder is, determined by how the fielder is able to get to balls hit in his vicinity.
ErrR (error runs): The number of runs above or below average a fielder is, determined by the number of errors he makes as compared to an average fielder at that position given the same distribution of balls in play.
UZR (ultimate zone rating): The number of runs above or below average a fielder is in both range runs and error runs combined.
UZR/150 (ultimate zone rate per 150 games): The number of runs above or below average a fielder is, per 150 defensive games.<!--QuoteEnd--><!--QuoteEEnd-->
I am troubled by the fact that I really do not know who grades every game. There also seem to be some trends developing in the data they provide, like penalizing outfielders that play in large outfields and over valuing outfielders that play in small outfields. Trying to objectively grade 16 games a day for six months every year seems like an almost impossible task to me. With that being said, this is the best attempt at giving some actual value to defense that I have ever seen. The difference between the most and least amount of runs scored per year is around 200 per year, the difference between the most and least runs allowed per team is usually around 250 runs per year. As fans we spend so much time with the players offensive numbers and give almost no value to the defense they bring to the table this helps a bit. To me this a flawed system that has a tremendous amount of use full data, but everything must be taken with a grain of salt.
Here are the definitions from fangraphs.
<!--quoteo-->QUOTE <!--quotec-->Fielding
DG (defensive games): The number of outs made by an average fielder at his position given the exact distribution of balls in play for that player divided by the number of outs an average player at that position makes per game.
exO (expected outs): The number of outs plus reached base errors that would be made by an average fielder given the distribution of balls in play while that fielder was on the field.
RngR (range runs): The number of runs above or below average a fielder is, determined by how the fielder is able to get to balls hit in his vicinity.
ErrR (error runs): The number of runs above or below average a fielder is, determined by the number of errors he makes as compared to an average fielder at that position given the same distribution of balls in play.
UZR (ultimate zone rating): The number of runs above or below average a fielder is in both range runs and error runs combined.
UZR/150 (ultimate zone rate per 150 games): The number of runs above or below average a fielder is, per 150 defensive games.<!--QuoteEnd--><!--QuoteEEnd-->
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