Defender Bob Harris has been allowed to join Fleetwood Town on-loan for the remainder of the Sky Bet League One season.
But the Blades have a 24-hour recall on the left-back who hasn't featured in the first-team since the beginning of December.
The defender, who missed the whole of pre-season and the opening three months of the campaign through injury, moves to Highbury in search of regular first-team football having only made seven appearances for United this season and boss Nigel Adkins feels it is a move that is in the best interest of all parties.
He commented: "Bob hasn't played much football this season, but he is now fully fit and needs games. We still have a big squad and, if necessary, we can have him back at 24 hours notice."