Melville was recalled from Triple-A El Paso on Monday.
Melville will join the Padres after being claimed off waivers from the Twins last month. He compiled a healthy 2.95 ERA and 1.15 WHIP in 76.1 Triple-A innings this season, though he struggled in his only major-league appearance, allowing five runs in 3.1 frames of work. Melville's worked mostly as a starter in the past, and it's safe to assume he'll primarily serve as a mop-up man out of the Padres' bullpen down the stretch.