Glossary

Batters – A list of sabermetric stats for batters that you may find on Baseball Professor

  • BABIP (Batting Average On Balls In Play) – A batter’s average on batted balls ending a plate appearance, excluding home runs. The league average typically hovers around .300.
  • EQA (Equivalent Average) – A measure of total offensive value per out, with corrections for league offensive level, home park, and team pitching. EQA considers batting as well as baserunning, but not the value of a position player’s defense. League average EqA is always equal to .260.
  • ISO (Isolated Power) – A measure of a hitter’s raw power, in terms of extra bases per AB. Its formula is ISO = (2B + (3Bx2) + (HRx3)) / AB
  • OPS (On Base Plus Slugging) – On-base percentage [(H + BB + HBP)/(AB + BB + HBP + SF)] plus slugging percentage [(TB/AB)]
  • SecA (Secondary Average) – A complement to batting average, which is a simple ratio of base hits to at bats. Secondary average is a ratio of bases gained from other sources (extra base hits, walks and net bases gained through stolen bases) to at bats. Secondary averages have a higher variance than batting averages. In modern Major League Baseball, a secondary average higher than about .500 is considered outstanding, and one below .200 is considered very poor. The league average SecA is typically similar to the league average batting average, in the range of .250-280.
  • SPD (Speed Score) – SPD is one of five primary production metrics used by PECOTA in identifying a hitter’s comparables. It is based in principle on the Bill James speed score and includes five components: Stolen base percentage, stolen base attempts as a percentage of opportunities, triples, double plays grounded into as a percentage of opportunities, and runs scored as a percentage of times on base. In the formulation of SPD, an average rating is exactly 5.0. The highest and lowest possible scores are 10.0 and 0.0, respectively, but in practice most players fall within the boundary between 7.0 (very fast) and 3.0 (very slow).
  • VORP (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.
  • WARP (Wins Above Replacement Player) – 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. Notice how fielding is taken into account. It should also 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.

Pitchers – A list of sabermetric stats for pitchers that you may find on Baseball Professor.

  • BABIP (Batting Average On Balls In Play) – A pitcher’s average on batted balls ending a plate appearance, excluding home runs. The league average typically hovers around .300.
  • BB/9 – Walks per 9 IP
  • EqERA (Equivalent ERA) – calibrated to an ideal major league where EqERA = 4.50. While a major league pitcher’s equivalent stats should not differ substantially from his actual numbers, a minor league pitcher’s equivalent stats undergo translation and may differ significantly. Equivalent stats also adjust for park effects, and the quality of a pitcher’s defense.
  • G/F – Ground ball to fly ball ratio
  • H/9 – Hits per 9 IP
  • K/9 – Strikeouts per 9 IP
  • K/BB – Strikeouts per walk
  • Park Adjustment – An adjustment made to account for the fact that some parks are easier to hit in than average, giving an advantage (in raw statistical terms) to hitters who play for that team. Park factors are always made relative to a league average of 1.00. The park adjustments in the BP are made only on the park factor for runs, averaged over five years.
  • PERA (Peripheral ERA) – A pitcher’s ERA as estimated from his peripheral statistics (EqH9, EqHR9, EqBB9, EqK9). Because it is not sensitive to the timing of batting events, PERA is less subject to luck than ERA, and is a better predictor of ERA going-forward than ERA itself. Like the rest of a pitcher’s equivalent stats, his PERA is calibrated to an ideal league with an average PERA of 4.50.
  • WHIP (Walks Plus Hits Per Inning Pitched) – A measure of a player’s efficiency of preventing runners from reaching base.

(Definitions taken from Baseball Prospectus)