Nigel Clough could be facing a selection headache at the weekend after two left-backs limped out of Monday's draw at Preston North End.
Despite Bob Harris and Matt Hill not being able to finish the game at Deepdale, the Blades picked up a point after a resolute defensive display.
The manager's attentions, though, have switched to Saturday's Sky Bet League One clash with table-toppers Wolves.
He commented: "Bob Harris felt the top of this thigh and then Matt Hill came on and with his very first run towards the corner flag he said his hamstring tightened up.
"It was a blow losing two full-backs within a few moments of each other and we will have to see how they are closer to the weekend. With regards to Hill, the hamstring has not 'gone', so we hope he won't be out too long."
After losing both Harris and Hill, Kieron Freeman filled in at left-back with Ben Davies coming on at right-back.
"Both Kieron and Ben did great jobs for us and we may have John Brayford back for Saturday, we'll have to see how he trains," added Clough.