One day after claiming the switch-hitting catcher off waivers from Atlanta, Kansas City announced that Pena had been designated for assignment to make room for Saturday's starting pitcher, Kyle Davies, on the 25-man roster.
As of Monday, there will be a 72-hour window for another club to claim Pena. If he isn't claimed, the Royals will have the option of assigning Pena to one of their Minor League clubs.
With the possibility that Miguel Olivo could become a free agent at the end of the season, the Royals would like to keep Pena in their organizational mix as they consider long-term plans.
"We're taking him off [the active roster] today and we'll just go from there," Royals manager Trey Hillman said. "There's a process, obviously, that you've got to go through."
Pena, 26, was 4-for-14 (.286) at the plate for Atlanta this year. Having played parts of four seasons for the Braves, Pena is familiar to Royals general manager Dayton Moore, who came from the Braves' organization two years ago.
Robert Falkoff is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.