Milone will pitch behind opener Erik Swanson during the second game of Wednesday's doubleheader against the Nationals, Ryan Divish of The Seattle Times reports.
Milone was initially listed as Seattle's scheduled starter for Wednesday's nightcap, but he'll instead serve as a bulk reliever. The southpaw has posted a 3.60 ERA and 0.70 WHIP in 10 innings over four appearances for the Mariners this year.