Manager Rob Thomson said Sunday that Harper has been held out the past few days with back stiffness and won't play Monday, but the slugger is expected to rejoin the lineup later in the week, Todd Zolecki of MLB.com reports.
It doesn't appear to be a serious injury, as Thomson said there is "zero" concern for Harper's Opening Day availability. Still, with less than two weeks before the March 28 opener, it's worth keeping an eye on the 31-year-old's status over the next few days.