Chris Wilder has boosted his defensive ranks once more with the purchase of a Championship defender.
The Blades have paid Brentford an undisclosed fee for 22-year-old Jack O'Connell, with the former England youth international penning a three-year deal at Bramall Lane.
Liverpool-born O'Connell was signed by Mark Warburton in February 2015 and made 18 appearances for the Bees in all competitions last term.
The versatile defender, who can operate at centre-back or left-back, has racked up over 100 senior starts, the majority of which came during highly successful loan spells with Rochdale.
During the 2012-13 campaign, O'Connell spent the full season at Spotland and captained 'Dale to promotion from League Two, previous to that he had also spent time with Rotherham United and York City.
Boss Chris Wilder is delighted to have captured O'Connell, who started his career at Blackburn Rovers.
The Gaffer commented: "I'm delighted that the Board have backed this signing because Jack is an exciting talent.
"He's young, hungry and has a considerable number of games under his belt at a good level, considering his age. We are delighted to add him to our squad and we are still working on getting one or two more into the building."
O'Connell is United's second signing of the week, following the arrival of fellow defender James Wilson and fourth in total with the services of Mark Duffy and Chris Hussey already secured in May.