He played in Major League Baseball (MLB) for the Toronto Blue Jays and Miami Marlins.

[1] As a sophomore, Shafer hit .300 with five home runs and 25 RBI, and posted a 1–1 win–loss record, 5.20 ERA, and 26 strikeouts in 272⁄3 innings.

[1] In his final season with the Gators, he hit .211 with one home run and 10 RBI, and went 1–0 on the mound with a 4.17 ERA and 27 strikeouts in 362⁄3 innings.

[4] During the offseason, Shafer pitched for the Salt River Rafters of the Arizona Fall League (AFL).

Shafer spent the majority of the year with New Hampshire, and earned a late-season promotion to the Triple-A Buffalo Bisons.

On August 19, 2018, Shafer was called up by the Blue Jays and made his debut the same day in relief against the New York Yankees, throwing a scoreless inning with a strikeout.

On March 8, 2021, Shafer signed with the Kansas City Monarchs of the American Association of Professional Baseball.

[17] On April 15, 2024, Shafer was hired to become the pitching coach for the Kansas City Monarchs of the American Association of Professional Baseball.