Castillo (groin) will start in right field Sunday in Triple-A Pawtucket's game against Syracuse.
Castillo made his season debut for Pawtucket in Saturday's doubleheader, playing both ends and finishing 1-for-6 with a walk and a run scored. His ability to play on back-to-back days suggests he's moved past the groin injury that sidelined him for a portion of Boston's Grapefruit League slate.