The Mets placed Diaz on the 15-day injured list Wednesday with a right shoulder impingement.
Left-hander Josh Walker was recalled from Triple-A Syracuse to take Diaz's spot on the 26-man active roster and in the New York bullpen. After blowing ninth-inning leads in four of his last five appearances, Diaz had already been expected to get a break from closing duties, and his injury will only further delay his opportunity to resurface as the Mets' preferred ninth-inning man. Reed Garrett and Adam Ottavino likely represent the best bets for saves out of the Mets bullpen while Diaz is on the shelf.