Nigel Clough says it was also a priority to strengthen United's midfield options this summer.
Clough was speaking after completing the signing of James Wallace from Tranmere Rovers for an undisclosed fee on Friday afternoon.
The Gaffer remarked: "James is a very good young central midfielder and he was out of contract.
"A compensation fee was agreed and he is the type of player we need to be in the market for.
"He will add extra competition to our midfield and that is an area where you need to be very strong in any division, but especially in League One."
The Blades boss is optimistic that Wallace will give United further options next term, as he competes with the likes of Chris Basham, Michael Doyle, Stefan Scougall and Stephen McGinn for a starting jersey.
Clough added: "We have plenty of good players in the middle of the park and once James gets into the team it will be about him keeping his place. He certainly gives us an extra dimension.
"You need a lot of energy in midfield, but we also have plenty of quality. We are also strong in the wide areas and that is pleasing at this stage of the close season."