Exit Velocity, Part II: Looking for a Repeatable Skill
In part one of this three-part series, we examined the (relatively strong) correlation between exit velocity and slugging percentage — and the (also relatively strong) correlation with individual wOBA, a solid proxy for offensive production at the plate. While there might be some debate over how important exit velocity is on offensive production — particularly when we dial down to an individual level — we know there is some relationship, and that relationship is enough to answer the next question, which is whether exit velocity represents a repeatable skill.
We first attempted to answer the question of whether exit velocity matters. Once we know that it matters, it is still incredibly important to try and determine if it is a skill. An appropriate analogy might be as follows: we know that pitcher BABIP against is important because when the BABIP is higher, the pitcher gives up more hits and runs. Unfortunately, we know a lot less about determining pitchers who can suppress BABIP or pitchers who seem to be prone to a high BABIP. We might believe that it is a repeatable skill; however, if it takes an incredibly long time to figure out who has the skill and who does not, then using a pitcher’s BABIP against to try and predict future performance is of limited use.