The Athletics recalled Barnett from Triple-A Las Vegas on Friday.
Barnett will start Friday's game against Cleveland, and Joe Rock has been optioned to Las Vegas in a corresponding move. Barnett has appeared in 18 games with the Athletics this season, making four starts, and owns an ugly 7.08 ERA, 1.62 WHIP and 38:24 K:BB across 40.2 innings. He's started each of his last four appearances with the club and has functioned as a starter in Triple-A, so Barnett should be stretched out.