The Blades have strengthened attacking options further on transfer deadline day by capturing Scottish international Barry Robson.
Hot on the heels of Jonathan Forte signing a loan deal for the remainder of the campaign, former Celtic and Middlesbrough player Robson has agreed a contract until the end of the current campaign and international clearance for the deal to be ratified was completed on Thursday.
Experienced midfielder Robson, 34, arrives in South Yorkshire after his contract with the Vancouver Whitecaps was cancelled by mutual consent earlier this month after a year in the MLS.
The 17-time capped Scotland international started his career at Inverness Caledonian Thistle before Dundee United recruited him in May 2003. He was then signed twice by Gordon Strachan, at Celtic and Boro.
Danny Wilson commented: "We have lost Nick Blackman to the Premiership but, fortunately, we have managed to bring in Barry at short notice on a deal until the end of the campaign.
"When someone of his experience and quality comes along you have to sit up and take notice and I'm delighted a deal can be completed, especially given the fact that he has been back in the country less than a week.
"He gives us options in offensive positions, he will score goals and be a supply line for others."
Robson, who will wear the number 19 shirt at Bramall Lane, is United's fourth signing of the January transfer window after securing the signatures of Danny Higginbotham, Jamie Murphy and Forte.