A Cursory Investigation of the Backup Slider
I wish I could come to you with news about the mass adoption of backup sliders from pitchers across the league. I also wish I could come to you with a shining example of even one player who has perfected the art of the effective mistake. There is no apparent analytical case that comes to mind; it’s largely just a fascination to me — the best hitters in the world swinging through the worst offering a pitcher could imagine throwing. Here’s an example:
Matt Wisler is the perfect guy to have here — someone who throws nothing but sliders making the biggest kind of slider mistake! And yet there are times when it just works. What I want to try to answer is what makes these mistake sliders click without diving into the rabbit hole of pitch sequencing. Are there particular characteristics of movement and velocity that make for better backup sliders?
First, we have to set guidelines on what a backup slider is. You know it when you see it, but it is more broadly defined as something that “hangs” when thrown to a batter of the same handedness. Sliders behave differently depending on whether they’re thrown inside or out, as shown by Eno Sarris on this site a few years back; those away gain almost half a foot of horizontal movement compared to ones thrown inside! Sliders need height to be considered mistakes, but the distinctions in horizontal movement are too vast for an outside-and-up slider to be as bad a mistake as one up but inside. For our purposes, let’s say that a backup slider is anything in the upper third of the strike zone, middle-to-in, in a same handedness matchup. Read the rest of this entry »
