Machado was promoted from Triple-A Rochester on Friday, Matt Weyrich of NBC Sports Washington reports.
Machado will return to the big leagues after being sent down Tuesday, filling in for Josh Rogers (shoulder) who was placed on the 15-day injured list Friday. The right-hander has produced a 5.40 ERA and 1.58 WHIP with 10 strikeouts over 13.1 innings in 12 appearances with the Nationals this season.