Centre-back Caldwell battled through illness to start last weekend's 5-2 defeat at Hull before coming off in the 37th minute and duly missed Tuesday's 1-1 draw at home to Blackpool, with the Scot returning to training for the first time on Friday.
Left-back Hancox sustained a hamstring injury against the Seasiders which saw his involvement cut short in the second half and he is now sidelined for three weeks.
Boss Lee Clark said: "It was a blow when young Mitchell had to come off with a tight hamstring. It's a bit of a nightmare for us, you just get things going the way you want them to and you get a setback."
Spanish defender Pablo remains sidelined through injury while leading scorer Marlon King has been ruled out for the remainder of the season with a knee problem but midfielders Keith Fahey and Darren Ambrose could be involved.