Diaz was recalled from Triple-A Syracuse on Friday, Tim Healey of Newsday reports.
The right-hander was sent down Wednesday, but he'll return to the major-league roster after Jake Reed (forearm) was placed on the 10-day injured list Friday. Diaz has made six relief appearances in the majors since Aug. 1, and he's recorded a 5.40 ERA and 1.35 WHIP in 6.2 innings during that span.