The Mets made the moves before Thursday night's game against Atlanta. Matsuzaka was put on the 15-day DL on July 26 with elbow inflammation.
Black received a cortisone shot on Wednesday. General manager Sandy Alderson indicated it would take a while before the right-hander feels any effect from the injection.
''Vic said that he had this issue once before,'' Alderson said. ''I think really we're responding not just to the diagnosis but to the treatment.''
''At some point we had to make a decision because we need another arm,'' he said. ''Trying to make it through to the end of the month with what we had just didn't look realistic.''