The Padres are expected to call up Diaz from Triple-A El Paso on Sunday, Kevin Acee of the San Diego Union-Tribune reports.
After being released by the Rockies on Aug. 16, Diaz signed a minor-league contract with the Padres 10 days later. He's gone 3-for-12 with three runs scored, one home run and six RBI across his three outings with El Paso, and he will join the Padres active roster when it expands to 28 players Sunday. Diaz will provide a third option at catcher behind Kyle Higashioka (illness) and Luis Campusano.