Smith recently resumed throwing bullpen sessions, but he's still experiencing back tightness and is without a clear timeline for a return from the 15-day injured list, MLB.com reports.
Smith had been contending with back issues for several weeks before the Royals placed him on the IL on Aug. 26. Though it's encouraging that Smith hasn't been shut down from throwing, he'll likely need the soreness in his back to subside a bit more before the Royals are comfortable bringing him back. It's unclear if Smith has a legitimate chance at being activated before the regular season ends Sept. 29.