Ben Heneghan says he is 'focused' on the challenge of forcing his way into Chris Wilder's squad after arriving from Motherwell on deadline day.
The Blades paid an undisclosed fee for the imposing centre-half, who began his career at Everton and Heneghan admits the move came out of the blue, but he is delighted it did.
He remarked: "It was a stressful day, but I was just glad to get here and get the deal completed.
"It was always on my mind to move back to England at some point, but I was only halfway through a two-year deal at Motherwell.
"But to know you are wanted and to know United have been watching is brilliant for me personally.
"The Gaffer had done plenty of background on me. He knew I was a hard-working lad and he knew plenty about how I play, which is nice."
Heneghan added: "It's a long-term deal, I have got a chance to put down some roots and now I can focus on trying to get into the team, it will be tough, but competition is good and it makes you improve.
"I like a battle, I'm good in the air and I like to stride out with the ball too, so if and when I get the call I need to be ready."