The Right Stuff Revisited: Another Attempt to Quantify Pitch Quality

The Right Stuff Revisited: Another Attempt to Quantify Pitch Quality

Photo by Kathryn Riley/Getty Images Pitching research has advanced by leaps and bounds over the last few years — Stuff+ needs to adapt. A few years ago, I introduced Stuff+ on these digital pages to help power the pitcher analysis in the series previews and elsewhere. It was an attempt to measure the raw stuff of a pitcher’s arsenal using the physical characteristics of their pitches. Back in 2019, this type of pitch evaluation was still a new frontier. Eno Sarris, Jeff Zimmerman, and a handful of others had dipped their toes into creating arsenal scores like this. Fast forward two years and the amount of research into what makes individual pitches successful has grown exponentially. The biggest leap forward has been a much deeper understanding of how the spin imparted on a given pitch affects its flight path. In 2020, MLB updated it’s tracking system from Trackman to Hawk-Eye, giving us much more detailed information about how a pitch travels from the hand to the plate. The result has been a huge leap forward in pitch research. It’s almost comical to look back on the components that were included and the way Stuff+ was calculated. I was using the data that was publicly available at the time, but as is the case with many things in baseball, we just didn’t fully understand the minutiae of the game. With more public data in hand, I figured it was time to update the way I calculate my Stuff+ scores to reflect the current research. Spinning Stuff+ 2.0 The biggest change to Stuff+ is the way I approach spin rate. Back in 2019, we knew that spin rate was highly correlated with velocity and movement and, generally, high-spin pitches resulted in high whiff rates. With Hawk-Eye cameras installed across baseball, we now have the ability to directly measure the spin axis of a given pitch. Before 2020, we had been inferring spin axis based on the movement of the pitch, but it turns out that pitches don’t often move like we expect them to based on the rate and direction of their spin when leaving the pitcher’s hand. This effect has been dubbed “seam-shifted wake” and the research into it has been gaining plenty of steam over the last year or so. Essentially, the idea is that seam-shifted pitches introduce a different type of spin to a pitch that affects the ball’s flight. A pitch’s spin direction will look one way out of the pitcher’s hand but the actual movement of the pitch when it crosses the plate suggests that the original spin direction

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