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Comparable Players are the backbone of a player's PECOTA. Only the twenty best comparables are listed here, but as many as 100 players may be used in the generation of his forecast if they are sufficiently comparable.
PECOTA compares each player against a database of roughly 20,000 major league batter seasons since World War II. In addition, it also draws upon a database of roughly 15,000 translated minor league seasons (1997-2006) for players that spent most of their previous season in the minor leagues. (When minor league comparables are used, they appear in ALL CAPS).
PECOTA considers four broad categories of attributes in determining a hitter's comparability:
1. Production metrics--such as batting average, isolated power, and unintentional walk rate for hitters, or strikeout rate and groundball rate for pitchers. 2. Usage metrics, including career length and plate appearances or innings pitched. 3. Phenotypic attributes, including handedness, height, weight, career length (for major leaguers), and minor league level (for prospects). 4. Fielding Position (for hitters) or starting/relief role (for pitchers). PECOTA doesn't require that a comparable hitter play the same defensive position; it is a factor that is evaluated along with many others, and assigned a relatively substantial weight. Consideration is also given to the 'similarity' between two positions; for example, a shortstop will be compared to a second baseman before he is compared to a left fielder.
In most cases, the database is large enough to provide a meaningfully large set of appropriate comparables. When it isn't, the program is designed to 'cheat' by expanding its tolerance for dissimilar players until a reasonable sample size is reached.
Comparable Players appears in the following BP Glossary Categories:
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