Hamm is dealing with a right shoulder strain with Double-A Erie, Sam Dykstra of MLB Pipeline reports.
He hasn't officially been placed on the injured list, but the nature of the injury suggests Hamm is closer to week-to-week than day-to-day. The 23-year-old righty logged a 4.88 ERA, 1.34 WHIP and 76 strikeouts in 83 innings across 20 starts at Double-A last year.