The Rangers optioned Santos to Triple-A Round Rock on Thursday.
Santos will head down to Triple-A after making his MLB debut Wednesday, when he gave up two earned runs on two hits and a walk while striking out one batter across two innings. His move to Triple-A will work as somewhat of a promotion, as he spent most of the first half at Double-A Frisco, posting a 7.44 ERA and 1.78 WHIP over 42.1 frames. Ben Peoples was selected to the active roster in a corresponding move.