Table of Contents

How Ratings are Calculated

The simulated performance of each pitcher and batter in a library is determined by the the player's basic probabilities (see How Basic Probabilities are Calculated) and several ratings.  These ratings and probabilities are also used by the computer manager to make decisions during a game or in the middle of a draft.  The game's core set of ratings help determine a player's ability to run the bases, bunt, field a position, and stay strong while pitching.  When the game engine needs to make a decisions about the outcome during the game, it may consult these core ratings and roll a virtual 1,000-sided die to determine the outcome.  In an effort to to make the inner workings of the game engine as transparent as possible, the virtual die rolls that determine the outcome are show in the Message Window during game play. 

Core Ratings

The following describes each of the four core ratings in more detail:

  1. Steal rating: This rating represents the probability that a runner will be able to successfully steal a base, assuming they were able to get a good lead.  The odds of getting a good lead are defined in the the General Options->Running dialog.  If a runner has met the minimum number of stolen base attempts required (as specified in the Normalize Options dialog) the steal rating is calculated as SB/(SB+CS).  However, if the runner does not meet the minimum number of required attempts, this rating is normalized (see Explaining Normalization).  This rating is also historically normalized (see Explaining Normalization for more information).
  2. Lead rating: This rating represents the odds that a batter will be able to get a good lead and attempt a steal.  The lead rating is based on how often a player attempts a steal when they are on first base and it is reduced if a left-handed pitcher is on the mound.  This rating it is calculated as (SB+CS)/(1B+BB) + GoodLeadAdj - LHPPenalty.  The GoodLeadAdj  and LHPPenalty are defined in the General Options->Running dialog.
  3. Bunt rating: This rating represents the probability that a runner will be able to successfully execute a sacrifice bunt.  With respect to bunting ability, batters are placed into three different categories: excellent, good, and poor.  Each category is assigned a success probability in the General Options->Hitting dialog.  The category that a batter is placed in depends on the number of sacrifice hits they had in real-life.  The number of hits required to be in a category is also defined in the General Options->Hitting dialog.
  4. Fielding rating: This rating represents the probability that a fielder will make an error while playing a position.  If a fielder has at met the minimum number of fielding chances required at a position (as specified in the Normalize Options dialog) this value is calculated as E/chances.  If the runner does not meet the minimum number of required attempts at a position, this rating is normalized (see Explaining Normalization).  This rating is also historically normalized (see Explaining Normalization for more information). 

    Finally, if the fielder has no fielding chances at a position, this value is calculated by reducing the average error rate (as specified in the current league average file) by a either a minor or major penalty.  If the player is being rated at a position that is similar to a position they have played, the penalty is minor.  If the position is very different than a position they have played the penalty is major.  The value for both minor and major fielding penalties are specified in the Normalize Options dialog. 

    A chart explaining how major and minor penalties are selected when playing out of position is shown below:

    Position Fielder Can Play
    Substitute Position   P C 1B 2B 3B SS LF CF RF
    P None Major Major Minor Minor Minor Major Major Major
    C Major None Major Major Major Major Major Major Major
    1B Minor Minor None Minor Minor Minor Minor Minor Minor
    2B Major Major Major None Minor Minor Major Major Major
    3B Major Major Major Minor None Minor Major Major Major
    SS Major Major Major Minor Minor None Major Major Major
    LF Major Major Major Major Major Major None Minor Minor
    CF Major Major Major Major Major Major Minor None Minor
    RF Major Major Major Major Major Major Minor Minor None
  5. Durability rating: This rating represents how many batters a pitcher can face before getting tired.  This value is equal to the total number of batters faced by the pitcher divided by the number of games played, or ( (IP * 3) + getH() + getBB() ) / G.

Draft Rating

The primary statistic used by the computer manager to select players during a draft (and in many game situations) is the Draft Rating.  The Draft Rating is a single measurement of the quality of a player and is visible on most of the statistical tables employed by Digital Diamond Baseball.  The game currently uses two different methods for calculating the draft rating: one for batters and one for pitchers:

  • The Batter Draft Rating: The batter's draft rating is calculated using the stolen base version of runs created, which was created by Bill James.  This statistic measures the number of runs a hitter contributes to his or her team.  The stolen base version of this statistic also takes into consideration a player's base stealing ability.  Because this number reflects the number of runs a hitter contributes, the larger the number the better.  This rating is calculated using the following formula:

        (H + BB - CS) * (TB + (0.55 * SB)) / (AB + BB) (where TB is total bases, which is calculate as 1B + 2(2B) + 3(3B) + 4(HR))
  • The Pitcher Draft Rating: The pitcher's draft rating is calculated using the fielding independent pitching statistic.  This statistic approximates a pitcher's ERA by eliminating the effect fielding may have played on the actual ERA.  Because this rating reflects the pitcher's ERA, the smaller the number the better.  This rating is calculated using the following formula:

        (13HR + 3BB - 2K) / IP + 3.10

Of course, the technique used to calculate the Draft Rating will have a major impact on computer managing and computer drafting, and every baseball fan has a different opinion about what should be used.  We feel the measurement we have currently implemented is a great first attempt.  However, ultimately we want you to be able to decide what algorithm the computer uses.  As a result, a top priority for a future release of Digital Diamond Baseball is to make the algorithm configurable.  We envision in the near future allowing the user to select from a variety of methods of calculating the Draft Rating.  We look forward to your feedback regarding the future development of our computer drafting algorithm!