Blackwell was without nine first-team players for last week's home defeat to Newcastle and then lost Kyle Walker to an ankle ligament injury and skipper Chris Morgan, who is suspended after reaching five yellow cards for the season.
Morgan's absence means he will not come up against Iain Hume - 12 months after his controversial aerial challenge left the Tykes striker with a fractured skull.
Defender Jordan Stewart strained his calf during the warm-up on Monday night and was forced to play due to the injury crisis, but now he has also been ruled out.
Gary Naysmith, Derek Geary (both knee), Richard Cresswell (ribs), Jamie Ward (broken wrist), Nick Montgomery (knee), Lee Williamson (back), Andrew Davies (knee), Andrew Taylor (thigh) and Paddy Kenny (drugs ban) are all still unavailable.
Blackwell could be forced to name some injured players on the substitutes' bench again after an unfit Williamson made up the numbers against Newcastle as his side chase a first win in seven league matches.
