Graduation Year


Date of Submission


Document Type

Open Access Senior Thesis

Degree Name

Bachelor of Arts



Reader 1

Richard Burdekin

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This thesis investigates the effect of Tommy John surgery on MLB starting pitcher performance for the 2017-2023 MLB seasons. The paper uses data from the sources Statcast ( and, focusing on various conventional and advanced performance statistics for MLB starting pitchers as well as their salary. Using the Ordinary Least Squares (OLS) regression model, the thesis measures the significance of the dummy variable Tommy John surgery on various pitching statistics to see how the surgery affects performance for MLB starting pitchers. The regressions measure the effect of Tommy John surgery on a pitchers era, wins, weighted on base average against, hard hit percentage, and salary. The regression analysis finds that Tommy John surgery has a significant effect on all the performance statistics except for pitcher era and that pitchers with Tommy John surgery experience an increase in pitcher wins and weighted on base average against, as well as a decrease in hard hit percentage. The thesis further determines that Tommy John surgery is significant in determining an MLB starting pitcher's salary, with pitchers that have undergone the surgery experiencing higher salaries. A final regression examined the different variables that are significant in determining if a pitcher had Tommy John surgery, with higher pitching velocity and higher average break on breaking pitches being significant indicators in pitchers with the surgery. The paper concludes that further research including relief pitchers and other statistics would increase understanding on the effect of Tommy John surgery on MLB pitchers.