Nationals manager Blake Butera said that Herz (elbow) won't make a rehab start Sunday with Single-A Fredericksburg as planned after experiencing forearm tightness following his most recent outing Tuesday, Spencer Nusbaum of The Athletic reports.
Just over 15 months removed from Tommy John surgery, Herz had looked good over his first three rehab starts between Fredericksburg and the rookie-level Florida Complex League, turning in a 1.17 ERA, 0.52 WHIP and 11:0 K:BB in 7.2 innings. The southpaw appeared to be tracking toward consideration for a spot in the big-league rotation upon his return from the 60-day injured list, but the setback will muddle his outlook. Herz will likely be shut down at least a couple of weeks before resuming mound work.