Alan Knill says United's management are delighted to have secured the signature of John Lundstram.
The Liverpool-born midfield joined the Blades on a three-deal from Oxford United on Tuesday afternoon and is a player the coaching staff at Bramall Lane have monitored for a long time.
Chris Wilder's number two commented: "We've seen a lot of him, firstly from his time at Everton, then recently whilst he has been at Oxford.
"He is a very good player and adds competition to our central midfield. We've got Coutts and Fleck, but we need more and John has come in to give us strength in that area."
Knill added: "We like the fact he started at the big club and has had to leave the big club and go and graft. He has played in League Two, League One and the Championship and we believe he can progress all the way.
"We've signed him to be a big player for the next three years and we believe we can develop him, so he's certainly one for the long-term."