Diaz was recalled from Triple-A Syracuse to serve as the 27th man in Saturday's doubleheader against the Nationals, Tim Healey of Newsday reports.
Diaz was sent to the minors at the end of May, but he'll be available as bullpen depth in Saturday's twin bill. He's made five relief appearances since returning to Triple-A and has posted a 4.26 ERA and 1.58 WHIP in 6.1 innings.