Barlow was optioned to Triple-A Omaha on Tuesday.
Barlow has been with the Royals all season, but his 6.19 ERA didn't make a case for him remaining there. His 31.3 percent strikeout rate is promising, though he walked too many batters (10.2 percent) and recorded a low 33.3 percent groundball rate. Jake Newberry was recalled to replace him in the bullpen.