This is a review of the MLB research conducted by Joe Rosales and Scott Spratt applying the Strike Zone Plus/Minus.
Every baseball game creates some controversy regarding the calls of strikes and balls. No one ever completely agrees with the umpire and umpires, being human, are not 100% accurate. It seems that some players in the MLB have a touch when it comes to getting pitches called as balls. This is often attributed to the catcher. While catchers definitely do have an influence, so does the pitcher, the batter, and obviously the umpire. The catchers use their catching skills, pitchers use their ability to place a pitch, batters use body language, and umpires use their judgment.
Aside from the four individuals, other variables also have an effect on the call. In order to isolate the amount an individual contributes it must be determined what effect these other variables have on the call. Seven variables are looked at in this study: pitch location, batter handedness, pitcher handedness, ball/strike count, pitch type, command of the pitcher or how close he is to hitting the catcher’s target, and if the pitcher is playing for the home or road team.
The seven variables were tested to determine which should be included within the model. Pitch location is the basis by which a ball or strike is called and therefore was the first variable included. Count and command showed the most significant variation, and consequently were also included. Command demonstrated a greater variation with horizontal distances than vertical distances in relation to where the catcher’s mitt was set so pitches were grouped by their horizontal distance from the catcher’s mitt. Batter handedness also shows a significant impact so it was the fourth variable added. The other variables had an insignificant impact and therefore were not included.
After each pitch was categorized by location, the other three variables were included in order to determine the percent likelihood that each pitch was called a strike. These strike percentages represent the Strike Zone Plus/Minus.
In order to maintain a balance between the requirement for both current data and legitimate sample size, a rolling four-year basis is used, meaning that the Strike Zone Plus/Minus will always be based on the pitch results going back four years from the current date. The Strike Zone Plus/Minus assigns a plus if a pitch is called a strike and a negative if the pitch is called a ball. From there it is determined how large or small the positive or negative value should be, which is based on how likely a pitch would be called a strike.
The process of categorizing an individual’s plus/minus is run through twice. The first time through it is simply determined if a player has a positive or negative value. The second time through determines what percentage is due to the individual player and which is due to the environment. Any environmental percentage is evenly divided among the four individuals and added on to their individual contribution. The second process is run multiple times until the change for each player becomes minimal.
Coaches can use this information to determine which pitchers, catchers, and batters have the greatest skill in influencing a call and analyse those players to isolate the skills used. These skills can then be taught to other players in order to increase their ability in this area. Coaches and general managers can use this model to determine the effectiveness of their players, especially catchers, in getting called balls rather than strikes. This information can then be used during salary negotiations and when looking at making trades. As not all teams place an importance on players with this skill, it might be possible for teams to pick up players with this skill at a lower cost.
An important note to remember is that while a pitcher wants a positive plus/minus rating, batters want a negative plus/minus rating.
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