The Mets optioned Diaz to Triple-A Syracuse on Wednesday, Mike Puma of the New York Post reports.
Diaz was a casualty from the active roster after the Mets needed to bring up Chance Sisco from Triple-A to serve as the backup catcher behind Patrick Mazeika in Wednesday's series finale in San Francisco due to No. 1 backstop James McCann (back) not being available off the bench. Since receiving a promotion from Syracuse on July 4, Diaz appeared in 13 games out of the New York bullpen, logging a 4.11 ERA and 1.30 WHIP across 15.1 innings.