This is Michael Rosen’s first piece as a FanGraphs contributor. You may have read his previous work at the site, including his article about the Kirby Index, a metric he created to measure command using release angles. He lives in Los Angeles and works as a transportation planner.

Earlier this year, I tried to solve the riddle of how Shota Imanaga threw his invisible fastball. The pitch had (and still has) a rare combination of traits: At the time of writing, only Imanaga and Cristian Javier threw fastballs from super flat vertical approach angles (VAA) with elite induced vertical break (IVB). A fastball with a flat VAA or high IVB plays a trick on the hitter’s perception; a fastball with both qualities becomes nearly unhittable, or invisible, when located at the top of the zone. I posed two questions in that piece: Why was this invisible fastball so rare? And what was Imanaga specifically doing to throw a fastball with these traits?

The first question can be answered, my research shows, by looking directly at release angles. Release angles reflect the direction that the pitcher is aiming the ball at release, which I wrote about at length in my article on the Kirby Index from May. That act of aiming — specifically, the direction the ball is oriented out of the pitcher’s hand — also affects the amount of backspin on a four-seam fastball. Read the rest of this entry »

George Kirby had Javier Báez right where he wanted him. It was October 3, 2022, the last start of Kirby’s excellent rookie year, and Kirby had Báez, the king of chasing sliders off the plate, in an 0-2 count. His catcher, Cal Raleigh, set up off the plate, suggesting that Kirby would be targeting the outer edge.

Kirby hit his target with a well-executed slider. And Báez, instead of whiffing, hit it out of the park.

Báez wasn’t fooled; at seemingly no point did he think that pitch was a fastball. And Kirby’s lack of deception — defined here as a lack of overlap between the horizontal release angle (HRA) of his fastball and slider — may have played a part. Read the rest of this entry »

On the first knuckleball thrown at Coors Field in 16 years, Matt Waldron hit home plate umpire Bill Miller right in the nuts.

Nobody — not Waldron, not his catcher Kyle Higashioka, not Miller — appeared to know where the ball was going. Despite Higashioka frequently (and understandably) struggling to track the flight of the ball throughout the rest of the night, Waldron delivered a career-best performance, allowing just one run over six innings.

Perhaps the most surprising part of his performance was the setting. Since 2008, knuckleballers have dodged outings at Coors Field, which sits 5,200 feet above sea level. Conventional wisdom dictates that knuckleballs at altitude are a bad idea, as Cy Young-winning knuckleballer R.A. Dickey told Dave Krieger back in 2012. Read the rest of this entry »

In the course of researching the haphazard nature of JP Sears’ fastball command for my blog Pitch Plots, I realized I was missing the answer to a fundamental question: Why does the ball go where it goes?

Specifically, I had no idea which variables determine the physical location where a pitch crosses home plate. My first guesses revealed nothing: a combination of velocity, extension, spin, and release height had no relationship to a pitch’s eventual location. If it wasn’t any of these factors, what could Sears change to throw his fastball to better locations?

I was missing the key variable: the release trajectory. Trajectory, as defined here, is not just release height and width but also the vertical and horizontal release angles of the pitch, which are not widely available to the public on a pitch-by-pitch basis.

The release trajectory, it turns out, explains nearly everything about the ultimate location of a pitch. Read the rest of this entry »