Blackburn was assigned to minor-league camp Monday, Susan Slusser of the San Francisco Chronicle reports.
Blackburn earned a promotion to the 40-man roster in November and impressed manager Bob Melvin with his arsenal, but a five-run outing in Cactus League play Friday essentially killed any chance he had at claiming an Opening Day spot. The 23-year-old could resurface with the big club as a spot starter or long man out of the bullpen later in the season, but it looks like he'll begin his 2017 campaign in a rotation role at either the Double-A or Triple-A level.