The Marlins sent Lopez to Triple-A Jacksonville on Saturday, Jordan McPherson of the Miami Herald reports.
With Johnny Cueto (illness) returning from the injured list Saturday, Lopez will head back to the minors to free up a spot on the roster. The 30-year-old reliever is out of minor-league options and will have to pass through waivers before he can reach Jacksonville. He's allowed 12 runs in 11.2 innings since joining the Marlins in July.