Machado was recalled from Triple-A Rochester prior to Sunday's game against the Marlins, Jesse Dougherty of The Washington Post reports.
Machado will take the roster spot of Erick Fedde, who landed on the 10-day IL with an oblique strain Sunday. Machado served as the club's 27th man during the July 12 twin bill against San Francisco but did not pitch in either game before being sent back to Rochester. The right-hander has posted a 2.63 ERA and 1.36 WHIP across 13.2 Triple-A innings this season.