Stuff or Not

The baseball pitching statistic known as Stuff+ compares the physical characteristics of a pitch (Release point, velocity, spin vector, movement profile) to the expected run value. In other words, how many runs are scored on a particular type of pitch? Every Stuff-type pitch grader uses a different combination of pitch variables, sometimes including pitch location, arsenal information, batter attributes (like handedness), and even pitch sequence. Usually, the ultimate goal is to apply a rating to a pitch, and ultimately grade a pitcher's arsenal. One thing lost in this grading approach is understanding how a specific kind of pitch can lead to specific outcomes. For example, sometimes you need a ground ball. How often does a particular sinker lead to a ground ball, and what tweaks to velocity, movement, release point or sequencing can make that pitch even more likely to result in a grounder? This link between pitch characteristics and batted ball types (or event types like whiffs) can have an outsized impact on calling pitches and managing games. The Stuff or Not app is designed to provide coaches and players easily accessible information about event type outcomes, and expected statistics like xAVG and xSLG, for different pitches. The app is built on data from over 5 million Division 1 (D1) college pitches and over 2.2 million Major League Baseball (MLB) pitches from 2022-2025. The app's dashboard screen makes it easy for players to input pitch characteristics and see D1 and MLB event outcome likelihoods. This dashboard is particularly useful for adding competition, and another dimension of coaching, to bullpen sessions. The heatmap screen allows the user to see how quickly, and in what direction, event type outcomes vary with changing pitch characteristics.