[7][8] Making his MLB debut, Hart allowed seven runs (five earned) on seven hits and three walks in two innings of work, taking the loss.

[10] With the 2020 Red Sox, Hart made four appearances (three starts), registering an 0–1 record with 15.55 ERA in 11 innings pitched with 13 strikeouts.

[12] Hart spent the 2021 season in Triple-A with the Worcester Red Sox; in 23 games (20 starts), he compiled a 4.22 ERA with 6–9 record while striking out 90 batters in 106+2⁄3 innings.

[13] He made 24 appearances split between Worcester and Portland in 2022, accumulating a 7-3 record and 5.25 ERA with 74 strikeouts in 82.1 innings pitched.

[15] Hart made one appearance for the Triple-A Lehigh Valley IronPigs, striking out one in a scoreless inning of work.

[20] On February 13, 2025, Hart signed a one-year, major league contract with the San Diego Padres that included a club option for the 2026 season.