But skipper Chris Morgan will return from suspension next week and on-loan Arsenal defender Kyle Bartley has recovered from food poisoning.
Blades coach Gary Speed said: "(Connolly) is a tried and tested full-back. Marcel (Seip) can play there and Nyron (Nosworthy) can play there too, but they are far more comfortable in the middle.
"Kyle wasn't feeling well enough to start on Tuesday night, so getting Paul in, who knows his stuff, means they can concentrate on their better positions.
"With Kyle and Morgs also being centre-halves it might mean we have some competition in there again, which can only be a good thing."