The modern baseball landscape is saturated with advanced metrics for evaluating pitchers. However, determining which of these stats are truly useful can often be a confusing endeavor. As a major league statistician, these are the analytics I refer to when gauging a pitcher’s effectiveness:
ERA+
Adjusted Earned Run Average, or ERA+, normalizes a pitcher’s ERA across the league by accounting for factors like ballpark and quality of opponent. A score of 100 is league average, meaning that a pitcher with an ERA+ of 130 is thirty percent better than the league average.
Like Adjusted OPS, ERA+ is an important metric because it helps contextualize pitcher performance. It also makes it possible to compare pitchers who pitch in vastly different run scoring environments.
Swinging Strike % and Whiff Rate
One manner of gauging a pitcher’s pure stuff is determining how often he misses bats.
Swinging strike percentage is calculated by dividing the number of swings-and-misses that a pitcher induces by total number of pitches thrown, while whiff rate is calculated by dividing swings-and-misses by total swings.
Both stats are useful for assessing how often opponents fail to make contact against a particular hurler.
Opponent Exit Velocity
Elite pitchers generally induce weak contact, and average opponent exit velocity can tell us which pitchers are the most difficult to square up. Hard-hit rate, the percentage of batted balls of 95+ MPH that a pitcher allows, serves a similar purpose.
Average Spin Rate
Spin rate, which is measured in revolutions per minute (RPM), represents the rate of spin on a baseball after it leaves the pitcher’s hand. The amount of spin affects the ball’s trajectory, and pitchers who combine elite velocity with a high spin rate are generally more effective. However, as written by MLB.com’s Mike Petriello in an article summarizing the first year of Statcast, “It’s not that either high spin or low spin is better, it’s that you want to be at an extreme on either end. Otherwise, your fastball is probably straight and hittable, as [Nathan] Eovaldi found.”
Searle’s Final Say
Basic stats like ERA and strikeouts are insufficient for accurately determining which pitchers are the best. Modern baseball is littered with hurlers who combine elite fastball velocity with ridiculous spin rates. As a result, the number of strikeouts across the majors has increased each year since 2008. Because today’s pitchers are so effective, we must compare their ability to generate whiffs and limit hard contact when evaluating their performance.
