Sheerin graduated from Exeter High School, just an hour from Philadelphia. As a senior, he piled up a staggering 101 strikeouts in 46.1 innings. Sheerin (7-3, 2.27) only allowed 19 hits and was voted to the All-County team in 2023. He led the Eagles to a 4-1 upset of second-seeded Gov. Mifflin in the opening round of the District 3-5A playoffs. Sheerin gave up one hit over 6.1 innings with eleven strikeouts.

Despite his size and statistics, Sheerin wasn’t heavily recruited out of high school. He attended Mount St. Mary’s and was named the MAAC Rookie of the Year in 2024. Sheerin set school records for strikeouts (109) and opponents’ batting average (.197). He made 18 appearances, including a pair of starts as a freshman. Sheerin only gave up 49 hits in 70 innings with a 4.76 ERA.

After transferring to LSU, Sheerin suffered a torn ACL while playing basketball during the summer. He missed the 2025 season with the Tigers. Sheerin worked exclusively out of the bullpen this spring. In 20 appearances, he racked up 58 strikeouts over 37.2 frames. Sheerin (3-2, 4.78) allowed 30 hits and earned five saves. “My delivery is very different and creates a lot of swing and miss. My fastball is my strength, but it’s my passion to compete that I think really makes the difference,” he replied. Sheerin’s massive frame and unique crossfire arm motion make him an intriguing prospect. He features a fastball in the mid-to-high 90s and a slider. “I want Phillies’ fans to know that every time I get to put on that uniform, it means the world to me,” emphasized Sheerin.