The others who were announced on the Surprise Rafters roster on Tuesday were right-hander Patrick Keating and left-hander Mike Montgomery; catcher Salvador Perez; second baseman Johnny Giavotella and first baseman Eric Hosmer, and outfielder Derrick Robinson.
All are on the Double-A Northwest Arkansas roster except Perez, who is with Class A Wilmington. Another pitcher will be added later.
Duffy, a top starting prospect, left Spring Training for personal reasons but later decided to return to pitching. In 13 games for three Minor League clubs this season, he's 4-3 and has a 2.98 ERA. For Northwest Arkansas, he's 4-2 with a 3.38 ERA.