Playing for Boston's Class A Advanced Salem affiliate on Thursday, Castillo went 0-for-2 with a walk.
Manager John Farrell said Castillo will see action in both center and right field once he starts playing in games. Mookie Betts, who has been a standout for the Red Sox in center all spring, might also play some right field when Castillo is in center.
• David Ortiz remained out of the lineup due to dehydration, and it could be a few days before he returns.
"It might not be Sunday. Associated with the dehydration is going to be some soreness, and we're trying to flush out some of that overall general soreness that he's dealing with," said Farrell. "He'll be out there when he's ready."
• Closer Koji Uehara is still out with a left hamstring strain, but he might start playing long toss on Friday.
The Red Sox are still hopeful he'll be ready to pitch on Opening Day.
Ian Browne is a reporter for MLB.com. Read his blog, Brownie Points, and follow him on Twitter @IanMBrowne. This story was not subject to the approval of Major League Baseball or its clubs.