Analyzing Baseball’s Spin Rate Revolution

Using data science to understand the increase in pitchers’ spin rates

Source: https://rapsodo.com/understanding-rapsodo-hitting-data-spin-rate/

What is the Spin Rate? Why is it Important?

Spin rates on fastballs have increased every year since Statcast data has been available with the exception of 2016–2017. Most of the attention on the issue has come in the wake of the 2019 and 2020 seasons which saw the largest increases in spin rate

The Foreign Substance Scandal

Bauer has been very outspoken on this topic, testing the effects of various substances on spin rate and urging the MLB to take the matter more seriously. He has also accused other top-tier pitchers such as Gerrit Cole (shown in the previous gif) of using foreign substances to improve his performance.

Methods and Data Collection

Analyzing the Spin Rate Distribution

Distributions of fastball spin rates from 2015–2021. Each distribution represents a sample of 5000 pitches
Shapiro test statistics and p-values for each year’s spin rates
Distributions of all fastball spin rates for the 2017 and 2020 seasons above 2500 RPM
The 10 most frequent pitchers in 2020 with a fastball RPM above 2900

Analyzing Pitchers’ Changes in Spin Rate

A violin plot displaying distributions of individual players’ average fastball spin rate changes between seasons
Pitchers who increased their spin rate 200 RPM+ across seasons

The Effect of Spin Rate Change on ERA

A scatterplot illustrating the relationship between change in spin rate and change in ERA across seasons
A model summary of the linear regression model relating spin rate change and year to the change in ERA

Conclusions

A CU Boulder student and data science intern who is passionate about baseball analytics!

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