The Athletics recalled Johnson from Triple-A Las Vegas on Saturday.
Johnson carries a hefty 7.29 ERA and 2.00 WHIP through 21 innings in the majors this season, but he'll rejoin the Athletics' bullpen after giving up just one run in 5.1 Triple-A innings since being sent down to Vegas on Aug. 19. Kade Morris was optioned to Triple-A in a corresponding move.