The 21-year-old, who has been capped for England at youth levels, is rated highly and has also been linked to Wolves.
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He told Sky Sports News on Monday: "Playing in the Premier League and Europe will be a dream for me at this stage of my career.
"I've played nearly 170 games. I'm just 21 and the Sheffield United fans know I've given my all in every game I've played."
The centre-back has made 166 appearances for Sheffield United since breaking through in the 2010-11 season.
He played 52 times for the club last term, scoring six goals as they made a run to the semi-finals of the FA Cup. That run was ended by Hull, though, who scored four times in the second half to win 5-3 at Wembley.