L’Oiseau: Creating aging curves for Statcast metrics

From Peter L’Oiseau at The Hardball Times on July 25, 2019:

MLB Advanced Media’s 2015 public release of Statcast metrics carried with it a lot of promise for the future of baseball analytics. It introduced exit velocity — how hard the ball is hit off the bat — and launch angle — the vertical angle above or below the horizontal plane parallel to the ground. These metrics are all over broadcasts now, because they are intuitive to a viewing audience. With launch angle and exit velocity, we’re talking about things fans can plainly see: where the ball is going and how fast it’s going there. These metrics are also useful for creating the expected statistics xwOBA and xBA, which do appear to have predictive power, at least for hitters.

Now that we have four and a half years of data at our disposal, we can get a good picture of how exit velocity and launch angle change as a player ages.

Aging curves are a crucial part of projections, affecting our expectations of how the future will come to pass. Setting expectations is the method we as fans use for knowing how we feel about the sport we’re watching. When Ketel Marte all of a sudden becomes an All-Star starter or Mike Trout sits atop the WAR leaderboard again, we know how to feel about it because we’ve set our expectations. Understanding aging in baseball creates more accurate expectations, which helps us feel validated more often but it will also increase the level of surprise we feel when we see the outlier cases on the tails of the distribution.

Read the full article here: https://tht.fangraphs.com/creating-aging-curves-for-statcast-metrics/

Originally published: July 25, 2019. Last Updated: July 25, 2019.