Couple of thoughts:
1) Minor is a right handed pitcher; Dalbec has been, shall we say, pretty weak against righties this season.
2) More likely. Dalbec had to come out of last night's game, seemingly with some heat related issue. He may not be over it yet and they are probably being cautious with him. As of right now, it appears to be 92 in Boston with a heat index of 99.