[12] On June 22, Shugart announced via Twitter that he would forego his final year at Texas in order to sign with the Red Sox.
[13] He signed with Boston on July 6,[14][15] and first pitched in mid-August for the Rookie-level Gulf Coast League Red Sox, where he made three appearances with a 1.80 ERA in five innings of work.
On March 22, 2019, MLB suspended Shugart for fifty games "after a second positive test violating the drug prevention and treatment program.
"[17][18] Shugart subsequently made his first appearance of the 2019 season on May 27 with the Greenville Drive of the Single-A South Atlantic League,[16] spending the remainder of the year there.
[19] For the 2021 season, Shugart returned to Greenville, now members of the High-A East, started 22 games and pitched to a 6–6 record, a 4.78 ERA, and 93 strikeouts over 105+1⁄3 innings.
[22] On August 4, he pitched two innings of a combined no-hitter alongside Michael Wacha and Andrew Politi versus the Durham Bulls.