The Cardinals optioned Fernandez to Triple-A Memphis on Tuesday.
Fernandez took the loss in Monday's game versus the Brewers, getting charged with three runs (two earned) without recording an out. He's pitched well this season with a 2.70 ERA and 20:7 K:BB over 13.1 frames, but the Cardinals are desperate for fresh bullpen arms. Fernandez should be back in the big leagues soon enough.