Santiago was placed on the 10-day disabled list Wednesday due to upper-back pain, Rhett Bollinger of MLB.com reports.
It's unclear where this injury stems from, though he did only last 3.1 innings in his last start, a loss to the Royals. Additionally, Santiago missed most of June with a shoulder strain and has a brutal 10.93 ERA over his last four outings, so this trip to the DL piles on to what has been a rough season for the southpaw. On the bright side, with the All-Star break approaching, the 29-year-old may only have to miss one start before he returns to the mound. Alan Busenitz will take his place on the active roster and Felix Jorge will likely assume his spot in the rotation.