Craig Alcock is the first permanent departure of the January transfer window, he joins Doncaster Rovers for an undisclosed fee.
The 28-year-old has been a virtual ever present for Rovers since signing on loan in November and has made ten appearances, helping Darren Ferguson's side climb in to the top half of the Sky Bet League One.
At Bramall Lane, the versatile defender made a total of 37 appearances after signing in the summer of 2014. His last game for United was in the victory over Doncaster back in September.
Manager Nigel Adkins has reiterated, on a number of occasions, the Club's intention to trim the size of the first team squad in this transfer window.