Shafer (elbow) was outrighted to Triple-A Buffalo on Friday.
Shafer was cast off the 40-man roster in order to free up a spot for one of the Blue Jays' younger prospects. The 26-year-old spent a majority of the 2018 season at the Triple-A level but posted a 3.24 ERA and 1.56 WHIP across 8.1 innings in the majors.