Casas is dealing with knee soreness but could be back in the lineup for Tigres del Licey in the Dominican League on Friday.
The 22-year-old received an MRI which showed no structural damage, so he may be able to retake the field after a couple days of rest. Casas made his big-league debut for Boston this year and had a .197/.358/.408 slash line with five home runs and 12 RBI in 27 games, and any injury is likely to be treated with caution since he's the organization's top prospect.