Quality of pitch

Quality of Pitch (QOP) is a statistic that measures the quality of a baseball pitch. QOP was developed by Jarvis Greiner and Dr. Jason Wilson of Biola University, in California, as a method to objectively measure the quality of a pitch. QOP is derived using a linear regression model based on the different components of a pitch.

Jarvis Greiner, one of the main contributors to the QOP measurement, was a film major and a pitcher for the Biola Baseball team in 2010. Greiner, while talking to his peers and family, realized that there wasn’t a standardized measurement for curveballs in general. In baseball games, Greiner heard commentators used phrases such as “dirty curveball” or “nasty slider” to describe curveballs. However, these descriptions were very general and did not provide real or usable information about the quality of the pitch. This made Greiner want to develop a standard method to measure and label the quality of pitches – making measuring pitches an objective process. This idea came into being during an Intro to Probability and Statistics class Greiner took at Biola University. In this class, Dr. Wilson required all of his student to conduct a statistics project. So, the very ambitious Greiner thought of combining film, baseball, and statistics, into this project.

Dr. Wilson saw potential in Jarvis’ idea and offered assistance and encouragement for him to develop the Greiner Indx. Jarvis had some of this teammates pitch for him in a room with markings marked on the side of the wall, then he proceeded to film the pitches of the pitchers. Jarvis’ baseball coach, John Verhoeven (Angels, White Sox, Twins) rated the quality of the pitches according to how difficult they were to hit on a scale of 0 to 100. Greiner watched the filmed pitches and obtained the measurements from the pitches, which were initial height, breaking point, max height, and final location. Greiner, along with his teammates, did this process for 30 pitches. These rated pitches were used to derive the initial version of the Greiner Index, which is the predecessor of QOP. In other words, all the different components of the pitch will ultimately determine the “quality of the pitch.” The formula for the QOP was derived using a multiple regression model. “The rise and loc coefficients are negative, while the break.point, vert.break, horiz.break, and MPH are all positive. This makes sense, because a rising pitch and bad location make for a low quality pitch whereas a big break and fast speed make for a good quality pitch” (Wilson).

The Greiner Index (GI) is calculated with the following formula:

GI = -2.51*rise +0.51*tot.break+1.88*break.point-0.47*loc
GI = -2.51*3 +0.51*.48+1.88*21.5.-0.47*8=53.6

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