Joe Sbarra of Burton Albion tackles Mark Duffy of Sheffield Utd: James Wilson/Sportimage

Football Insider claim that Duffy’s contract, which expires next summer, will not be extended and his spell at United, which has brought two promotions since he joined in 2016, could be nearing its end.

United have not yet publicly commented on the report. Duffy was absent from United’s squad for their pre-season friendly at Northampton Town on Saturday. Chris Wilder’s Blades face Chesterfield tomorrow evening at the Proact, as their preparations for the Premier League season continue.

"It [the new season] is not too far away now," Duffy said earlier this month, when he last faced the media on United’s pre-season tour of Portugal.

Sign up to our Sheffield United newsletter The i newsletter cut through the noise Sign up Thanks for signing up! Sorry, there seem to be some issues. Please try again later. Submitting...

“We're preparing right and we want to be as fit as we can. It's the best league in the world and we want to be ready."

Osborn, who can play in midfield or at wing-back, was identified as a target for the Blades following their promotion to the Premier League.

The 24-year-old is in the last year of his contract at the City Ground, and Forest are willing to cash in this summer – rather than lose him for nothing in 2020.