The MVP Machine: How Baseball's New Nonconformists Are Using Data to Build Better Players

by Ben Lindbergh

Over the course of the regular season, though, both Kelly and Hembree had slowly lost their nasty sliders. Relievers who throw a lot of sliders, Bannister says, tend to release them with their hands slightly turned to the side, as if they’re throwing a football. That hand position imparts extra spin to the slider compared to holding the hand more square to home plate, which adds extra hop to the fastball. When the season started, Kelly and Hembree had their hands at an angle and threw spin-efficient sliders with less hop on their heaters, but they both began to suffer from the same affliction. “As the year went on, for whatever reason, their hand[s] [were] getting more and more square on their fastball[s], and they were getting more and more carry on their four-seamer[s], and we started to see them lose their sliders,” Bannister says. The wipeout pitches they’d been throwing in April had devolved into “baby cutters” that weren’t missing many bats. There was one happy by-product of this unintended alteration: pitchers who throw with their hands square to home also tend to have better curveballs. And so, Bannister says, “We actually saw Joe and Heath’s curveballs getting better while their sliders were getting worse.”