The Royals optioned Zobac to Double-A Northwest Arkansas on Saturday.
Zobac was awarded a spot on Kansas City's 40-man roster during the offseason, but he'll return to Double-A to begin the new year. The 25-year-old righty posted a 7.68 ERA and 1.91 WHIP over 36.1 innings at Northwest Arkansas last season but pitched 2.2 scoreless frames this spring.