Danny Duffy (elbow) will begin a rehab assignment with Double-A Northwest Arkansas on Sunday. He'll throw 60 pitches for the Naturals. Making his way back from Tommy John surgery, Duffy will surely require the full 30 days on his rehab assignment. Assuming the results are there and his arm strength is back, he should be added to the Royals' rotation in late June. The left-hander is worth stashing on the DL if you have the roster space.