Two players have departed Bramall Lane, one on loan and one on a permanent basis.
The Blades have agreed a loan deal for John Brayford to join Burton Albion.
Boss Chris Wilder explains: "This is an opportunity for John to return to the Championship and, of course, he has worked with Nigel Clough on a number of occasions previously.
"This loan enables us to reinvest in other areas before the end of the transfer window. I feel we already have cover in that area of the pitch and we'll look to strengthen in the coming days."
Brayford was signed from Cardiff City in 2015 following an impressive loan spell in 2014. Injuries have curtailed his progress in recent years but he has made a total of 68 appearances for the Blades and scored four goals.
Meanwhile, United have released Martyn Woolford to enable him to join another club.
In total, Woolford made 34 appearances for United in all competitions during the 2015/16 campaign.