Delighted Blades boss Kevin Blackwell said: "He's only 20 and a full international. He has shown glimpses of the real potential that enabled Bristol City to sell him (to Wigan) for £2million.
"David had set his heart on a move here, is prepared to look for a house in the area and we are showing the same commitment to bring him in."
The Blades have also landed Luton midfielder Matthew Spring on a season-long loan while Malta international keeper Justin Haber has arrived from Greek side Haidari on a two-year deal.




