Castro made two appearances for the Orioles out of the bullpen during their four-game series with the Red Sox over the weekend, tossing three scoreless, no-hit innings while walking three and striking out one.
After keeping the Royals off the board for 4.2 innings in a mop-up outing May 10, Castro had been tabbed to replace Chris Tillman (back) in the rotation after the latter was placed on the 10-day disabled list. Castro was lined up to make his first start last Wednesday against the Phillies, but a postponement ultimately prevented that from happening. The Orioles then appointed Triple-A Norfolk righty David Hess for Sunday's game in Boston when a fifth starter was required, resulting in Castro's window for joining the rotation coming to a close. Castro will likely get an opportunity to start games for the Orioles at some point this season, but it's uncertain when that might happen with manager Buck Showalter seemingly content to stick with Hess as the fifth member of the rotation for now.