Hearn was optioned to Triple-A Round Rock on Tuesday.
The left-hander pitched behind an opener twice after being recalled by the Rangers on July 15, and he fared well, with two earned runs allowed and a 10:3 K:BB across 7.1 innings. However, it wasn't enough to stick in the rotation with Dane Dunning (ankle) returning from the injured list. Hearn's performance could earn him more opportunities later in the year.