Zerpa was recalled by the Royals on Friday.
Zerpa has spent the entirety of this season so far with Double-A Northwest Arkansas, though he's pitched at the big-league level before, throwing five scoreless innings his major-league debut at the tail end of last season. In nine starts this year, he owns an unimpressive 4.79 ERA, though his 24.5 percent strikeout rate and 6.0 percent walk rate make for a somewhat promising combination. It looks as though he'll be pitching in a bullpen role for now, as it was reliever Collin Snider who was optioned in a corresponding move.