Replacement Level
Replacement level is one of the most commonly used baselines against which sabermetricians value player performance. However, the term frequently causes confusion, as there are many different definitions of it in use.
Bill James was the first to define replacement level, doing so in his early Baseball Abstracts. Initially he set replacement level at that of a player with a .400 Offensive Winning Percentage, but decided too many players were below the threshold, so he lowered it to .350.
Replacement level is sometimes confused with VORP, a statistic developed by Keith Woolner and popularized by the Baseball Prospectus. In fact, VORP is just one of many specific formulations that compare player performance to some definition of replacement level.
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Definitions of Replacement Level[edit]
There are many different specific definitions for replacement level, but while the exact numerical level it is set at may vary, there are several broad definitions that are used as guides for setting it.
Freely Available Talent (FAT)[edit]
The FAT concept assumes that there is a minimum level of production teams can easily add to their roster for the league minimum salary, either by calling up players from their farm system, trading with other organizations, or signing unwanted free agents. Assuming this level of production really is freely available, there's no reason for any player whose true talent is below this level to receive any playing time.
Sustenance Level[edit]
Sustenance Level is considered to be the level of performance at which a player becomes likely to lose his job. Clifford Blau and Phil Birnbaum have each published articles for By the Numbers attempting to find the sustenance level empirically.
Progressive or Time-Dependent[edit]
Other analysts have proposed definitions of replacement level that are time-dependent, increasing over time due to the greater variety of options available to teams to make roster moves. For example, if a starting pitcher was injured just prior to a game, he would have to be replaced by someone on the active roster. However, the team could then fill his next start with a AAA pitcher, or by acquiring a marginal pitcher from another club. In the long run, he could be replaced by a free agent or a prospect. written about this idea, referred to it as "progressive replacement level".
