Sullivan, only a freshman at Louisville, finished his first collegiate regular season without allowing a hit. His longest appearance came against Northern Kentucky when he tossed two innings and also recorded a career- high three strikeouts. 

A three-year letter winner while at Eastern High School of Louisville, Kentucky, Sullivan was ranked as the 12th best player in Kentucky and overall No. 1 left-handed pitcher in the state by Perfect Game for the class of 2017. Gavin was also named to the 2017 All-State team and helped the Eastern Eagles to a regional semifinal. His favorite sports team is the Oakland Raiders, and his favorite candy bar is Snickers.