Newman had pitched only 7 1/3 innings in four appearances since his callup on Aug. 10. He had no decisions and a 7.71 ERA. The move leaves the Royals with no left-handers on the Major League staff.
Kansas City also placed Luke Hochevar on the 60-day disabled list to allow Duckworth to be added to the 40-man roster. Hochevar went on the DL with a rib-cage contusion last week.
Manager Trey Hillman said that the move effectively shuts Hochevar down for the season. He added that it made perfect sense, because Hochevar would have only gotten two or three more starts, and the team didn't want to take any chances with his future.
Hochevar finishes his first full season in the big leagues with a 6-12 record and a 5.51 ERA.
Max Utsler is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.