Glossary: Frequently Requested Definitions

It was conceived of by both Tom Tango and Clay Dreslough, the latter of who called it Defense-Independent Component ERA. At BP, we are including hit batters in the walks term. The constant we use is both league and season specific - in other words, a pitcher in the American League will have a different FIP constants than a pitcher in the National League. This differs from the presentation of FIP on sites such as Fangraphs, which use one constant for both leagues in each season.

Full article by Colin Wyers.

Combining estimates of runs allowed and our estimates of outs generated, a measure that looks like RA is produced, called "Fair RA", or FRA:

Fair RA = Est_Runs / (Est_Outs/3) * 9,

where...

Est_Runs = H%*H_RUN + IF_AiB% * IF_AiB_RUN + GB% * IF_GB_RUN + OF% * OF_RUN
Est_Outs = H%*H_OUT + IF_AiB% * IF_AiB_OUT + GB% * IF_GB_OUT + OF% * OF_OUT

TAV considers batting as well as baserunning, but not the value of a position player's defense. The TAv adjusted for all-time also has a correction for league difficulty. The scale is deliberately set to approximate that of batting average. League average TAv is always equal to .260.

Equation:

1993 and beyond
TAv = 0.260 + (Runs Above Average/Plate Appearances)*0.9

True Average is now a linear-weights based system and a full entry is forthcoming. For now, check Colin's introduction to TAv here and here

Value Over Replacement Player. The number of runs contributed beyond what a replacement-level player at the same position would contribute if given the same percentage of team plate appearances. VORP scores do not consider the quality of a player's defense.

See also RARP.

Wins Above Replacement Player, level 1. The number of wins this player contributed, above what a replacement level hitter, fielder, and pitcher would have done, with adjustments only for within the season. It should be noted that a team which is at replacement level in all three of batting, pitching, and fielding will be an extraordinarily bad team, on the order of 20-25 wins in a 162-game season.