The Nationals optioned Machado to Triple-A Rochester on Monday.
Machado was sent to the minors over outfielder Andrew Stevenson, who sticks with the big club after Washington reduced its active roster to 26 men following Sunday's pseudo-doubleheader with San Diego. Following his July 11 call-up from Triple-A, Machado appeared in two games out of the bullpen and gave up three earned runs over 1.2 innings.