How Variety and Repetition Impact Pitching and Hitting Performance

How does arsenal size and usage impact pitcher and hitter performance?

At Oyster Analytics, we normally stay away from pitch evaluation, since there are about ten thousand stuff+ models out there and nearly the same number of people working on visualizing and analyzing Savant data in almost every combination. That’s fantastic to see, but it also makes it an area we’re less inclined to pile into.

With that said, today, we’re taking a trip along one of the less-traversed roads in the vast network of pitch analysis. We’re not making any claims about the value of individual pitches, but are instead here aiming to demonstrate how variety and repetition in pitch sequencing shapes hitter performance and pitcher longevity (both in games and in counts).

By now, we all know that pitchers tend to get worse the more they see hitters, with starters often getting pulled before their dreaded third trip through the order. But can the severity of that decline be altered by pitch selection? Is there a difference between facing a batter for the third time if you’ve got six pitches to throw at him vs. if you’ve already shown him each of your three offerings multiple times? Do batters get better within counts after seeing what a pitcher has to offer and getting their eyes on the same pitch multiple times?

In a word, yes. Generally, the more times a batter sees a pitch, the better they do against it–even controlling for time through the order. Conversely, the more times a pitcher throws the same stuff in a game and within a plate appearance, the worse they tend to perform. You could stop reading now, but this broad overview obscures a lot of meaningful nuance. Here, we highlight six key findings from our analysis.

Note: This analysis uses Statcast data from 2021-2024, starting pitchers only

1. Multiple Shapes of Breaking Stuff Increases Overall Longevity

2. A Few Changeups a Day Keeps the Bullpen Away

3. Larger Arsenals = Slower Drop Off

4. Emphasizing Variety in Pitch Calling Gets the Most Out of Pitchers

5. Throwing Gas is Great, But Its Advantage Fades Within Plate Appearances

6. Novelty Matters Most for Changeups and Breaking Balls

1. Multiple Shapes of Breaking Stuff Increases Overall Longevity

Generally, pitchers who can show batters multiple shapes of breaking stuff fare better as the game goes on. To us, this tracks logically: if a batter can know exactly what movement he should expect as soon as he identifies spin, he’s probably more able to adjust to that pitch than if there are multiple potential movement profiles he could face. What’s more, as we’ll discuss later, hitters generally fare better against breaking balls the more they see them–having two different breaking balls enables pitchers to show less of each one to each batter throughout the game.