Blackburn was called up as the Athletics' 29th man for Saturday's doubleheader against the Mariners.
Blackburn will start the second game of Saturday's twin bill, so his temporary promotion to the major-league roster comes as no surprise. He'll be making his 2020 debut during the penultimate game of the regular season after posting a 10.64 ERA and 2.09 WHIP over 11 innings in 2019.