Fields came to the Royals on Nov. 5 with second baseman Chris Getz in the trade that sent third baseman Mark Teahen to the White Sox. Fields, in 79 games for the Sox last year, had seven homers, 30 RBIs and a .222 average.
Ka'aihue spent all last season with Triple-A Omaha and hit 17 homers with 57 RBIs and a .252 average. He tied for the Pacific Coast League lead with 102 walks.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.