"This series [manager] Ned [Yost] wanted a left-handed bat," Moore said.
Yost also said he preferred Fuentes' versatility.
"He's a guy who can play all three outfield positions," Yost said. "He will be in the mix."
Yost also indicated that the reason he was using right-handed-hitting Paulo Orlando in right field against A's right-hander Sonny Gray in Friday's series opener, as opposed to left-handed-hitting Jarrod Dyson, had nothing to do with Dyson.
"I just wanted to see Paulo tonight," Yost said.
Fuentes, the cousin of former Royal Carlos Beltran, was hitting .444 through six games at Triple-A Omaha. The 24-year-old Fuentes is ranked No. 20 among all Royals prospects.
Jeffrey Flanagan is a reporter for MLB.com. Follow him on Twitter at @FlannyMLB. This story was not subject to the approval of Major League Baseball or its clubs.