The Athletics optioned Blackburn to Triple-A Las Vegas on March 7.
With Frankie Montas back after missing most of the second half of 2019 while suspended and youngsters Jesus Luzardo and A.J. Puk expected to become fixtures in the Athletics' rotation this season, Blackburn was quickly dismissed from the competition for a starting role with the big club. He'll likely serve as a depth option in the minors for most of 2020 unless injuries reopen an opportunity for him at the big-league level.