United have given Nick Blackman the green light to sign for a Premiership club.
The striker joins Reading for an undisclosed fee, signing a three-and-a-half deal. Blackman, who arrived from Blackburn Rovers last August, leaves for Berkshire having scored 14 times in 33 appearances for the Blades.
"From our position, it is virtually impossible to hold people back when the Premiership comes calling and this is a great opportunity for Nick," said Blades chief Danny Wilson.
"He wants to play at the best possible level, we knew that when we signed him, and he goes with our best wishes. He is a student of the game and will keep learning his trade at Reading."