Blackburn (forearm) was transferred to the 60-day disabled list Thursday, Susan Slusser of the San Francisco Chronicle reports.
This move clears a spot on the Athletics' 40-man roster for the addition of Trayce Thompson, who was claimed off waivers from the Yankees on Thursday. Blackburn was hoping to resume throwing sometime this week but was shut down after experiencing renewed soreness in his forearm. He'll now be sidelined until at least the end of May. In the meantime, Daniel Gossett will remain in Oakland's rotation until Blackburn is healthy, though Trevor Cahill looms as a potential replacement once he builds up his arm following a delayed start to spring training.