The Nationals are expected to recall Perales from Triple-A Rochester on Wednesday, Kyle Williams of TheBanner.com reports.
The 23-year-old righty will get his first big-league opportunity after posting a 3.64 ERA and 1.30 WHIP over 96.1 innings at Triple-A. Perales has worked primarily as a starter this season but will likely begin his MLB career in the bullpen after pitching two innings or fewer in each of his last four minor-league outings. He'll replace Jake Bird on the active roster.