Machado was recalled from Triple-A Rochester on Saturday, Jessica Camerato of MLB.com reports.
The 29-year-old was sent down Friday but will rejoin the Nationals' bullpen a day later after Evan Lee (shoulder) was placed on the 15-day injured list. Machado has made 17 relief appearances in the big leagues this year and has posted a 5.48 ERA and 1.52 WHIP in 23 innings.