In 2019, Sheehan played in the New England Collegiate Baseball League for the Danbury Westerners where he was an All-Star.

[4] The Los Angeles Dodgers selected Sheehan in the sixth round of the 2021 Major League Baseball draft.

[5] After signing with the team he was assigned to the Rookie-level Arizona Complex League Dodgers to start his professional career before being promoted to the Low-A Rancho Cucamonga Quakes and then a second time to the High-A Great Lakes Loons.

[13] Sheehan was expected to compete for a spot in the Dodgers rotation to start 2024, but was slowed in spring training by shoulder soreness and began the season on the injured list.

[14] On May 15, Sheehan underwent Tommy John surgery to repair the ulnar collateral ligament in his elbow, shutting him down for the rest of the season.