Triple-A Norfolk placed Zimmermann on its 7-day injured list Sunday with a hamstring injury, Rich Dubroff of BaltimoreBaseball.com reports.
Zimmermann presumably suffered the injury during his most recent outing for Norfolk on Saturday. The 29-year-old lefty remains on the Orioles' 40-man roster but has pitched exclusively at the Triple-A level so far this season, logging a 4.35 ERA, 1.48 WHIP and 34:13 K:BB across 39.1 innings.