Norwegian Erik Tonne has left United on a permanent basis, subject to international clearance.
The 22-year-old has signed for Sandnes Ulf in his homeland, after the Blades took up the option to recall him for a loan spell with Hamkam.
United were forced to end his stint with Hamkam, in order to make the permanent transfer possible in the current transfer window.
Tonne, who joined the Blades in September 2010, failed to establish himself in the first-team, although he regularly impressed for the reserves.
He made his debut against Middlesbrough in the Championship in April 2011, but at the end of that season the Blades were relegated to League One.
Under Danny Wilson, Tonne made a positive start to the following season, scoring in the Johnstone's Paint Trophy at Burton, before getting his first league goal against Bury in front of the Kop. He later had a loan spell at York City.
Having not featured for the first-team last season, Tonne returned to his homeland, signing for Hamkam on an eight-month loan deal in March.