Blackwell has no other new injury or suspension problems but revealed one of his squad is struggling with a knock.
Striker Darius Henderson will sit out the last game of a three-match ban and long-term absentees Gary Naysmith and Ryan France (both knee) and Derek Geary (ankle) remain sidelined.
Marcel Seip returned to the substitutes' bench at Crystal Palace, but was not used, while Henri Camara, Ched Evans and James Harper, all second-half replacements on Saturday, are pushing for returns to the starting line-up.
The Blades have lost five of their last eight league games and aim to bounce back from the 1-0 defeat at Palace in a bid to make up lost ground on the top six.
