Austin Riley and the slider

Photo by Rich von Biberstein/Icon Sportswire via Getty ImagesSliders are tough. In 2010, the league threw just about 13 percent of its pitches as sliders. That year, the run value of a slider for a pitcher was 0.56 per 100 sliders thrown, the highest among all pitch types, and the only breaking pitch with a positive value. I don’t bring this up to mislead you: pitch-level values are a strange beast, because pitchers use their arsenals to set up and/or bamboozle hitters, and the slider may only have a positive value because it’s well set up by a fastball or similar. In any case, though, sliders were good, perhaps because they weren’t thrown very often, but they were good nonetheless. Fast forward to 2019. Slider usage has jumped substantially, and now sits above 18 percent (the gain has come mostly as the expense of sinkers; four-seam fastball usage has actually increased since 2010 as well). The usage increased year-to-year nearly every time, aside from a small drop in 2012 and a slightly bigger fall in 2014. Between 2018 and 2019, the slider rate increased by 1.5 percentage points, the bigger rise ever. Despite the increased usage, the value of a slider hasn’t really changed, from +0.56/100 in 2010 to +0.51/100 in 2019. The lowest value in this stretch was 0.46/100; the highest was 0.67/100. The slider’s value last season ranked it on par with the splitter, which tends to be thrown way less (only one to two percent of pitchers are splitters) and is more volatile year to year: 0.53/100 in 2010, 0.54/100 in 2019, minimum of 0.03/100, maximum of 0.54/100.

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