Blackburn was added to the A's 40-man roster Friday.
The 22-year-old had to be added for Rule 5 protection. He was traded from Seattle to Oakland last week in exchange for Danny Valencia -- marking the second time Blackburn was traded in less than a four-month span. The results were strong for Blackburn at the Double-A level in 2016 (3.27 ERA, 1.21 WHIP), but he doesn't have dominant stuff as evidenced by his career 6.2 K/9 in the minors.