Machado was optioned to Triple-A Worcester on Friday.
Machado has served mainly as a middle reliever for the Nationals this year, and he's posted a 4.57 ERA and 1.43 WHIP in 43.1 innings over 38 appearances in the majors. However, he'll head to Rochester as part of a set of moves to make room on the active roster for Tyler Clippard and Jake McGee.