Castro is unavailable with a sore knee, Roch Kubatko of MASN Sports reports.
It's unclear when Castro picked up the injury or how long it will keep him sidelined at this point. With just four games left and the Orioles out of playoff contention, it wouldn't be surprising if the young right-hander didn't pitch again this season. Castro owns a 3.96 ERA, 1.45 WHIP and 57:50 K:BB across 86.1 innings this year.