Gallen was scratched from his scheduled start Monday against Oakland with right lateral forearm soreness, Nick Piecoro of The Arizona Republic reports.
Forearm issues are among the more worrisome problems for a pitcher, as they can sometimes be the first sign of a serious injury which requires major surgery. Whether or not that's the case with this particular problem remains to be seen, but even a very minor setback at this stage of spring would likely see Gallen open the year on the injured list. Per Steve Gilbert of MLB.com, Gallen felt the issue while swinging a bat rather than throwing, which is potentially cause for optimism, but there's a limit to how optimistic one should be when it comes to pitchers and arm troubles.