Hearn was recalled from Triple-A Round Rock on Tuesday, Joseph Hoyt of The Dallas Morning News reports.
Hearn was demoted last week but will rejoin the Rangers on Tuesday with Jon Gray (oblique) headed to the injured list. Hearn will remain in the bullpen despite the open rotation spot, as he's pitched well in relief over his last three outings with a 1.59 ERA and 1.15 WHIP across 11.1 innings.