"They're both day to day," manager Jim Leyland said Friday afternoon. "Neither one of them will perform today."
Jackson was walking about the Tigers clubhouse with his abdominal area wrapped to try to promote healing of the strain he suffered on his final swing Wednesday night.
Valverde was in noticeably good spirits in the clubhouse, and said he felt good. However, he wasn't quite ready to return yet. Friday marked his third straight game out since leaving Tuesday's ninth inning at Chicago with a lower back strain.
In both cases, the injuries are the type the Tigers don't want to aggravate. If they do, they could lose two key cogs for quite a while.