Howard was optioned to the Phillies' alternate site Wednesday.
Howard's first major-league appearance of the season came in a one-inning relief stint during Tuesday's doubleheader against the Mets. He allowed a run on two hits, walking one and striking out one. He's still seen by the Phillies as one of their top pitching prospects and he's likely to join the active roster for good at some point this year, but it's not clear when that time will come.