The Mets placed Diaz (knee) on the 60-day injured list Thursday.
Diaz's move to the 60-day IL was fully expected after he recently underwent surgery to address a tore patellar tendon in his right knee, an injury he sustained while celebrating Team Puerto Rico's win over Team Dominican Republic in the World Baseball Classic earlier this month. With Diaz facing an estimated six-month recovery from surgery, he appears unlikely to be available during the regular season, and even a return in October or November if the Mets make a deep playoff run seems implausible. Manager Buck Showalter has yet to name a new closer in Diaz's absence, though veteran relievers David Robertson, Adam Ottavino and Brooks Raley look to be the most likely candidates to pick up saves.