Right-hander Brendan Girton attended Shattuck High School in Shattuck, Oklahoma, where he posted a cumulative 2.84 ERA over the course of his varsity career there. Named to the Oklahoma All-State team and considered a high priority high school follow by scouts and evaluators, Girton went undrafted in the abbreviated 2020 MLB Draft and honored his commitment to Texas Tech instead.
The right-hander mainly pitched out of the bullpen in his first year with the Red Raiders. Appearing in 18 games, making two starts, he posted a 5.47 ERA in 24.2 innings, allowing 21 hits, walking 19, and striking out 23.