Hernandez was placed on the 10-day injured list Saturday with a left calf strain, Jesse Dougherty of The Washington Post reports.
Josh Palacios was recalled to replace Hernandez on the active roster. It's not entirely clear when this issue cropped up, though Hernandez had been out for three of four games prior to this move, so it may have been lingering. Hernandez will be eligible to return Aug. 30 should he prove ready.