The Nationals recalled Alvarez from Triple-A Rochester on Sunday.
The left-hander has a 4.66 ERA, 1.20 WHIP and 27:10 K:BB across 19.1 frames in four starts for Rochester and will now get a look in the big-league bullpen. The Nationals are starting PJ Poulin as an opener Sunday before turning to primary pitcher Miles Mikolas, after which Alvarez could be called upon to provide some more length.