United's first business of transfer deadline day is to sell Stephen Quinn to Hull City.
The Irishman joins the Tigers for an undisclosed fee.
The homegrown midfielder has chalked up over 250 appearances - including 50 last season - after making his league debut for the Blades in the Premiership in 2006.
Blades chief, Danny Wilson, told sufc.co.uk: "Stephen has been a great servant to Sheffield United and we wish him well - Hull City have got a fantastic player on their hands.
"We have really enjoyed working with him but things move on in football and this is great opportunity for him."