[1] As a junior, Shepherd was sidelined by a forearm laceration that forced him to miss three weeks,[1] but he returned to a relief role in nine games, following with nine starts.

[3] Shepherd started his professional career in 2014 with the Class A Short Season Lowell Spinners, where he was 4–3 with a 4.05 ERA in 16 games, working mostly as a long reliever in 33⅓ innings.

[3] But Shepherd spent much of the year with the Class A-Advanced Salem Red Sox, posting an 0–2 record with a 3.61 ERA and six saves in 28 games, including a 6.57 strikeout-to-walk ratio (46-to-7) in 52+1⁄3 innings.

[3] Later in the year, he also pitched well in the Arizona Fall League with the Scottsdale Scorpions, appearing in 11 games, while going 1–1 with a 3.97 ERA and one save in 11+1⁄3 innings.

[3] Shepherd opened 2016 with the Double-A Portland Sea Dogs, where he was 1–1 with a 1.80 ERA and seven saves in 14 appearances, including a 0.80 WHIP and .140 batting average against, while striking out 39 and walking 10 in 30 innings.

[5] He was designated for assignment when Sandy León went on paternity leave and the Red Sox added Oscar Hernández to its roster on May 17.

[8] Shepherd's five-day odyssey ended when he was claimed off waivers by the Baltimore Orioles and optioned to the Triple-A Norfolk Tides on May 22, 2019.

[17] Shepherd made 26 appearances (17 starts) for the Triple-A St. Paul Saints, posting a 9–6 record and 5.33 ERA with 68 strikeouts in 104.2 innings pitched.