The Athletics optioned Blackburn to Triple-A Las Vegas on Sunday.
Blackburn served as the 26th man for Saturday's doubleheader with the Rangers and started the first game. He lasted only three innings, allowing five runs on five hits and three walks en route to taking the loss. The performance wasn't good enough for the Athletics to justify keeping Blackburn around the next time a fifth starter is needed, so he'll head back to the minors and rejoin Las Vegas' rotation.