The Royals recalled Pennington from Triple-A Omaha to serve as their 27th man for the second game of Wednesday's doubleheader with the Cardinals.
Pennington will give the Royals a fresh arm out of the bullpen for the nightcap before he likely heads back to Omaha on Thursday. The 26-year-old lefty previously made his big-league debut last week in Colorado, retiring both of the batters he faced.