The Royals optioned Spence to Triple-A Omaha on Wednesday.
The Athletics traded Spence to Kansas City in February, and after surrendering eight earned runs over seven innings during spring training, he will report to Triple-A to begin his tenure with his new organization. The right-hander owns a 4.77 ERA and 1.40 WHIP across 236 innings in his big-league career and may be recalled later in the season to provide long-relief help.