The Mets activated Castro (illness) ahead of Wednesday's game against the Orioles, Tim Healey of Newsday reports.
The Mets sent Franklyn Kilome back to the alternate site to make room on the 28-man roster for Castro, who will be available out of the bullpen for the Mets' series finale with his former team. Before Baltimore traded him to New York on Monday, Castro had missed a couple of days with a sinus infection, but the Mets' decision to activate hm suggests he's moved past the illness.