Blades boss David Weir is unsure on the severity of Febian Brandy's hamstring injury, which the striker sustained in Saturday's loss at Bradford City.
The Walsall man was replaced by Joe Ironside early in the second-half at the Coral Windows Stadium, visably in discomfort, as he limped off the field.
Weir also explained his reasoning behind the substitution of youngster Callum McFadzean, as he called for the Blades to become stronger in their approach.
The Gaffer said: "Febian came off to make sure we didn't make things any worse with his hamstring, so we will assess him in the next couple of days. It is too early to comment further at this stage.
"Callum was withdrawn at half-time to enable us to get some experience on the field at what I felt was a crucial time after the restart and Callum understood when we spoke to him.
"It is a tough environment for everyone, especially the youngsters, but we have to develop that mental toughness to get better and we have to do that both individually and collectively."
When questioned about adding to his squad, Weir added: "We are always looking to improve the squad and that is two-fold. We have to improve the players we already have and add to the squad if possible.
"Recruitment is a continual process, we are always looking and monitoring the situation but I don't want to say too much more at the moment."