Sheffield United transfer news: Pre-season injury could change Blades' priority in window

Shackleton began as a central midfielder at first club Leeds United but spent the majority of what little game-time he had last season at full-back, mainly on the right.

When Shackleton joined the Blades on a free transfer at the start of the summer, they were still hoping to keep Jayden Bogle but his move in the opposite direction marked the 24-year-old as the most likely starter on the right of defence.

That has been called into question after Shackleton injured his knee in the Blades' penultimate pre-season friendly, a 2-1 win at Rotherham United.

"He's turned his knee, twisted his knee," explained manager Chris Wilder.

“He's got to go for a scan and fingers crossed it isn't too serious. Because we can't afford injuries at the best of times.

"I want to keep the squad fit and healthy but he's gone for a 50-50 and just twisted his knee, so there's nothing you can really do about that – an injury in a competitive game.”

With George Baldock released to join Panathinaikos at the end of last season and the versatile Ben Osborn moving to Derby County, the Blades' most senior specialist right-back is Femi Seriki, a 22-year-old who struggled to make an impact in a Rotherham United side at a low ebb.

Seriki made just two Championship starts after joining the Millers on loan in February. Rotherham finished bottom of the table last season.

Seriki has previously had loan spells with the Blades' sister club Beerschot, Boston United and Rochdale, but only played regularly for the latter.

So far this summer the Blades' signings have been of good quality, but few in number.

Callum O'Hare was impressive at Coventry City, Kieffer Moore has great Championship pedigree and Harrison Burrows was League One's player of the year last season.

On the back of Sam McCallum's arrival, the Blades now have two new left-backs but only five new players with Cameron Archer, Oli McBurnie, Max Lowe, Daniel Jebbison, Wes Foderingham, John Egan, Oliver Norwood and Chris Basham joining Bogle, Baldock and Osborn in leaving.

"We need to move and hopefully we will do this week," said Wilder.

“But Harrison coming in makes us stronger and hopefully we'll have a really good career at Sheffield United. His CV speaks for itself at his age and the next step was coming to play in the Championship. And hopefully a successful Championship side.”

The Blades are at Huddersfield Town on Friday, their final pre-season game before they open their Championship season at Preston North End on August 9.