Seattle and Atlanta had been cited as possible landing spots for the versatile backup outfielder who hits lefthanded pitching well.
The Mariners have needed to add another righthanded bat, so Denorfia fits the bill there.
The return for the Padres is right-handed pitcher Stephen Kohlscheen and outfielder Abraham Almonte.
Almonte, 25, hit .198/.248/.292 with five doubles, one homer and three steals in 27 games for the Mariners this season. In 72 games for Triple-A Tacoma, Almonte is hitting .267/.333/.390.
Kohlscheen, a 6-foot-6, 25-year-old righty, has a 2.70 ERA, 1.11 WHIP and 55 strikeouts in 56 2/3 innings in 38 relief appearances across Double-A (23 games) and Triple-A (15 games) this season.
Denorfia can handle all three outfield positions, though he's best suited on the corners. He's a platoon option with lefties Endy Chavez and/or James Jones.