The Nationals recalled Parker from Triple-A Rochester on Tuesday.
He's absorbing the roster and bullpen spot vacated by Jackson Rutledge. Parker boasts a 16:3 K:BB over 13.1 innings in his first three starts with Rochester this season, though that's come with a 6.08 ERA. The lefty will give the bullpen some length behind Tuesday's scheduled starter, Miles Mikolas, who's lasted a total of just 7.1 frames over his last two starts.