Kremer strained his left oblique a couple weeks ago and isn't expected to throw for another two weeks, Roch Kubatko of MASN Sports reports.
The injury was apparently incurred as the pitching prospect was working out in preparation for spring training. Kremer and the team seem to be downplaying the severity of the issue, though oblique injuries are notorious for having somewhat lengthy recovery times. A more concrete timetable for return will likely come forth once he's able to get back to throwing.