Kansas City acquired Butera from the Los Angeles Angels last month to back up Salvador Perez when Kratz went on the disabled list with plantar fasciitis in his left foot. Kratz had been on an injury rehabilitation assignment with Triple-A Omaha.
Kratz and Butera are both out of options, which meant the Royals had to choose between the two backups. Kratz was hitless in four games earlier this season, while Butera has fared little better offensively but has been solid in handling the Royals staff.
Kansas City was off Thursday before opening a three-game set in St. Louis on Friday.