The Washington Nationals placed reliever Victor Arano on the 15-day injured list Sunday with a right shoulder strain.
The designation is retroactive to Friday for the 27-year-old right-hander, who is 1-1 with a 4.50 ERA and one save in 43 appearances this season.
The Nationals recalled right-hander Andres Machado from Triple-A Rochester in a corresponding move.
Machado, 29, is 1-0 with a 4.57 ERA in 38 relief appearances this season with Washington.