The Guardians optioned Heuer to Triple-A Columbus on Monday.
Heuer will cede his spot in the bullpen and on the active roster to right-hander Shawn Armstrong (groin), who was reinstated from the 15-day injured list in a corresponding move. After being recalled from Triple-A last Wednesday, Heuer made a lone appearance during his stint in the big leagues, striking out two batters and allowing one run on three hits and one walk in two innings in Sunday's 10-3 win over the Reds.