Maurer and Buchter were expected to arrive at Comerica Park during Tuesday's game vs. the Tigers. Cahill was expected to arrive late Tuesday night.
"They give us a lot more depth," Yost said. "I've got several guys now who fill in for Kel if he goes several days in a row."
The Royals, who played Monday night with a 24-man roster, optioned right-hander Jake Junis to Triple-A Omaha to make room on the 25-man roster for Maurer and Buchter.
The Royals will have to make another roster move sometime Wednesday to make room for Cahill.