Removing the League Average Baseline From Defensive Metrics

I have always wanted to create an defensive metric that doesn’t adjust to the league average. Using Retrosheet data, I have made my first stab at it. I plan on making some small improvements and eventually having data available on all players. Here is an exert from my first article at Royals Review explaining in more detail the new metric:

For years, my one issue with the current defensive metrics is they attempt to show how a player is doing compared to the league average at a position. This method helps to give run values to the defense for inclusion into complete value metrics like WAR. The problem is the pool of full seasons of playing time at each position is limited to 30. If a couple of excellent defensive players get hurt or a player is moved to another position, a player’s value may change quite a bit even though they may be creating the same number of outs (example from a few years ago when I looked at this issue with some shortstops).

The first key to solving this problem is to get a year-to-year baseline of each position. It would show if all the defenders at a position are making more or less outs than the year before. Since I don’t have access to any of the good play-by-play data that is used to create UZR, I created a simple metric which looks at the number of outs a position creates (I will call it Out% in this article because I am basically too lazy to type it out every time). Basically, It measures the player’s range. It doesn’t take into account turning double plays, digs at 1B and OF assists. Here is a graph of the percentage of all batted balls that the position turns into an out:

Fielding_spectrum_medium

The percentage of outs changes year-to-year, but generally stay within a 1% range. A big drop in fielding happened in the mid-90′s. Using metrics set to the league average, a short stop who made an out at the 12% level each season in his career would be above league average in 1996. By 2000, he would be below league average. His skills may seem in decline, instead the other SS in the league were improving.

2 thoughts on “Removing the League Average Baseline From Defensive Metrics

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