Baseball Prospectus Glossary

Difference between actual wins and W1. A positive number means the team has won more games than expected from their statistics.

Difference between actual wins and W2. A positive number means the team has won more games than expected from their statistics.

Difference between actual wins and W3. A positive number means the team has won more games than expected from their statistics.

Delta-hits. The number of hits above or below what would be expected for this pitcher.

Defense-adjusted ERA. Not to be confused with Voros McCracken's Defense-Neutral ERA. Based on the PRAA, DERA is intended to be a defense-independent version of the NRA. As with that statistic, 4.50 is average. Note that if DERA is higher than NRA, you can safely assume he pitched in front of an above-average defense.

How much a pitcher is underrated by Adjusted Pitching Runs (DIFF = ARP - APR).

Days Missed Per Injury. The average number of days missed per team injury.

Double plays, turned or hit into.

The percent of the time the double play opportunities (DP_OPPS) were converted into double plays (DP)

The number of double play opportunities (defined as less than two outs with runner(s) on first, first and second, or first second and third).

DRA needs a week or two to get started each year but is up and running for good by May, and often well before.

DRA is BP's flagship pitcher run estimator. It estimates the rate at which a pitcher "deserved" to give up runs, and includes estimates for the uncertainty around that rate.

Deserved Run Average (DRA) uses a collection of multilevel models to estimate the most likely contributions of pitchers to the run-scoring that occurs around them. Unlike other component metrics, DRA considers (and adjusts) for park, opponent, and, when helpful, framing, temperature, and pitch type as well. DRA achieves significant improved reliability over both raw pitcher statistics (like ERA) and other pitcher run estimators. DRA estimates include uncertainty estimates, making it easier to compare players to one another and to appreciate the stability of DRA's estimates, even early on in the season. In general, a pitcher's DRA, plus or minus one standard deviation (DRA_SD) encompasses at least 70% of the "true" DRA values for that pitcher.

DRA- (pronounced "DRA Minus" and sometimes written as "DRA-Minus") rates pitchers by how well they compared to their peers rather than by an amount of predicted runs allowed in a given season. Knowledgeable baseball fans are familiar with statistics like this. Common examples include FIP-, ERA-, and wRC+. The formula for DRA-Minus is DRA / DRA_mean * 100

DRA-Minus ("DRA–") As noted above, we've received multiple requests for a "minus" version of DRA, something that rates pitchers by how well they compared to their peers rather than by an amount of predicted runs allowed in a given season. Knowledgeable baseball fans are familiar with statistics like this. Common examples include wRC+ and ERA-. The idea is to put an average player for each season at 100, and then rate players by how much they vary from the average. By rating every pitcher by how good (or poor) he was by comparison to his peers, we can make fairer comparisons across different seasons and different eras. These comparisons aren't perfect: We can't make baseball 50 years ago more diverse or force today's players to endure the conditions of 50 years ago, but metrics like DRA– allow comparisons of pitchers across seasons and eras to be much more meaningful.

The formula for DRA-Minus is DRA / DRA_mean * 100

Unlike cFIP (which considers only the three true outcomes), DRA– will not have a forced standard deviation. The two numbers (which are otherwise both scaled to 100) can still be compared, but be mindful of that distinction. For both cFIP and DRA–, lower is better.

See: http://www.baseballprospectus.com/article.php?articleid=26613

Pitcher WARP computed using DRA instead of FAIR_RA.

Replacement level used for a particular pitcher in computing WARP based on DRA.

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Number of runs saved - compared to replacement level - by this pitcher, taking into account DRA, DRA_REP_RA, and innings pitched.

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DRC+ is the Deserved Runs Created for a batter, scaled to a 100-based index. It tells us how valuable a player's offensive contribution is by assigning appropriate credit to plate appearance outcomes and applying contextual factors like park effects and opponent quality.

Learn more about DRC+ at our DRC+ Showcase page.

Traditional metrics compromise accuracy in two ways: (1) they summarize play outcomes in which players were involved, not player contributions to those outcomes; and (2) they treat all outcomes as equally likely to be driven by the player, even though no one believes that is true.

DRC+ addresses the first problem by rejecting the assumption that play outcomes equal player contributions, and forces players to demonstrate a consistent ability to generate those outcomes over time to get full credit for them. DRC+ addresses the second problem by recognizing that certain outcomes (walks, strikeouts) are more attributable to player skill than others (singles, triples). DRC+ gives more weight to extreme performances in the former (because they are probably meaningful) and less weight to extreme performances in the latter (because they are less likely to be meaningful). By addressing these two deficiencies in existing metrics, DRC+ ends up being substantially more reliable and predictive than any other baseball hitting metric. (The PA-level opponent and park adjustments don’t hurt either). The Top 15 undervalued players are not “undervalued” in the sense that they are hidden Hall of Famers; they get undervalued by OPS / wOBA / SLG / wRC+ / whatever because those metrics do not weight each event by the likelihood it was driven by the player himself, as opposed to random variance.

A player like Alberto Callaspo has somewhat extreme numbers in metrics DRC+ considers uniquely likely to be driven by the player: healthy walk rates and exceptionally low strikeout rates. Callaspo saved runs every year, on average, by striking out very infrequently. He was above average in walks for a while, although not every season. One consequence of not striking out so much is that he was hitting more singles, and consistently gets credit for hitting more singles than average. The point isn’t that Callaspo is some great player: it is that DRC+ better understands how “real” his contributions were than other metrics, because the latter make no effort to distinguish the various aspects of his game. It brings the same, more sophisticated perspective to other players also.

Deserved Runs Above Average - Runs above average for a hitter (RAA) based on the DRC+ model.

Deserved Runs Above Average - Runs above average for a hitter (RAA) based on the DRC+ model. This is used in the computation of Batter WARP. An introduction to the DRC+ statistic is here: https://www.baseballprospectus.com/news/article/45432/why-drc/

Deserved Runs Prevented (DRP) is BP’s metric for assessing fielder performance.

DRP is a top-level statistic that collects and sums the various ways that a defender can impact a play. This equation is generally dominated by the player’s range (RDA, or Range Defense Added), outfield assists (OFA), the rate at which defenders prevent baserunners from advancing (BRR_ARM), and the collected contributions of catcher defense (CDA, or Catcher Defense Added).

A player's defensive wins above replacement, as listed on his PECOTA card, and accounting for the value of his position and the quality of his defense. Analagous to FRAR.

Days eXpected Lost -- used as an estimate of how many days a player is expected to miss due to an injury or illness. For starters, five days equals one start.

The date the player returned from the injury.

The date the player suffered the injury.

How many days the player missed due to the injury.

Defensive Efficiency = 1- (H-HR)/(AB-SO-HR+SH+SF)

Def Eff, or Defensive Efficiency, is the rate at which balls put into play are converted into outs by a team's defense. Def Eff can be approximated with (1 - BABIP), if all you have is BABIP, but a team's actual Def Eff is computed with

1 - ( H - HR ) / ( AB - SO - HR + SH + SF )

the Team Audit Standings use the latter formula.

Alternately, it will be seen some places (including some past editions of Baseball Prospectus) computed as 1 - ((H + ROE - HR) / (PA - BB - SO - HBP - HR)), which comes out slightly lower in most instances.

Here is an example of the Defensive Efficiency spectrum based on the 2011 season:

Excellent - Tampa Bay .735
Great - Texas .722
Average - Toronto .710
Poor - Pittsburgh .700
Horrendous - Minnesota .693

Defense, as listed in a player's PECOTA card, provides the player's number of defensive games played, primary position, and fielding runs above average (FRAA) with a given team in a given season.

The number of hits above or below average for this pitcher, based on his own number of balls in play and his team's rate of hits (minus home runs) per ball in play; (H-HR) - BIP * (team (H-HR)/BIP). Essentially, the Voros McCracken number. For a team, Delta-H should be zero. Positive numbers signify more hits allowed than expected ("bad luck," if you believe pitchers have nothing to do with the outcome of a BIP), negative numbers mean fewer hits than expected ("good luck").

The number of runs, more or less, that a pitcher allowed, compared to his statistics. The pitcher's statistics (such as hits, walks, home runs) are run through a modified version of the equivalent runs formula to get estimated runs. Again, positive is "bad luck," negative is "good luck."

The number of wins, more or less, that a pitcher won, compared to estimated wins. Estimated wins are derived from the pitcher's actual runs allowed and team average run scoring. Here, a positive number is "good luck," negative is "bad luck."

The Depth Charts page compiles pertinent team data based on PECOTA projections and the latest Depth Charts update.

Users can access each team's individual depth chart as well as get an overview of how the teams are expected to perform in wins, losses, runs scored, runs allowed, and other vital statistical categories.

Diagnostics are a series of metrics designed to estimate the probability of certain types of changes in production and playing time; see the individual entries for additional detail.

Difference between RS/G and RA/G. A positive number means a team is scoring more runs than they're allowing on average.

Plate Differential - This statistic shows how far apart back-to-back pitches end up at home plate, roughly where the batter would contact the ball. This includes differentiation generated by pitch break and trajectory of the ball (which includes factors like gravity, arm angle at release, etc.).

Plate Differential - This statistic shows how far apart back-to-back pitches end up at home plate, roughly where the batter would contact the ball. This includes differentiation generated by pitch break and trajectory of the ball (which includes factors like gravity, arm angle at release, etc.).

Release Differential - When analyzing pitchers, we often talk about consistency in their release point, pointing to scatter plots to see if things look effectively bunched or not. This stat measures the average variation between back-to-back pitches at release.

Release Differential - When analyzing pitchers, we often talk about consistency in their release point, pointing to scatter plots to see if things look effectively bunched or not. This stat measures the average variation between back-to-back pitches at release.

Tunnel Differential - This statistic tells you how far apart two pitches are at the Tunnel Point—the point during their flight when the hitter must make a decision about whether to swing or not (roughly 175 milliseconds before contact).

Tunnel Differential - This statistic tells you how far apart two pitches are at the Tunnel Point—the point during their flight when the hitter must make a decision about whether to swing or not (roughly 175 milliseconds before contact).

Each league has been given a difficulty level, based on the performance of players in that league compared to the same players' performance in other seasons. The reference difficulty level was defined by the trend line of the National League from 1947 to 2002, and extended backwards to 1871. The difficulty adjustment is the ratio between the actual difficulty level and the reference level.

The percentage of times a team wins their division in the simulated seasons.

Drop Rate is the percent chance that a player will not receive any major league plate appearances in a given season, based on comparables who disappear from the dataset entirely. Because of the conventions PECOTA uses in selecting comparables, the Drop Rate is always assumed to be zero for the current year, but it is an important consideration in a hitter's Five-Year Forecast.