Hayes, 28, was claimed off waivers from the Miami Marlins on Nov. 2. He has been a backup catcher in Miami the past four seasons. Hayes has struggled in the batter's box, where he has a career batting average of .217 in 143 games. He has also struck out 118 times in 357 career plate appearances. Hayes is seen primarily as a defensive catcher, having thrown out 26 percent of would be base-stealers, but has also played outfield and first base in emergency situations in his career.
Hayes joins starter Salvador Perez as one of two catchers on Kansas City's 40-man roster. Former backups Brayan Pena and Adam Moore were designated for assignment on Tuesday. The Royals have filled their 40-man roster, so they will be unable to make major league moves without first clearing roster space.