Kieron Freeman could join Portsmouth on a permanent basis after finishing last season on loan with the League Two club.
The defender was among seven players transfer listed by new manager Chris Wilder nearly a fortnight ago and is thought to have held preliminary discussions about a return to Fratton Park next term.
Freeman, aged 24, made seven appearances for Paul Cook’s side but missed their play-off semi-final against Plymouth Argyle through suspension.
Wilder is planning a major overhaul of United’s squad after replacing Nigel Adkins at the helm with Dean Hammond, Paul Coutts and Martyn Woolford also among those declared surplus to requirements.
Signed by Adkins’ predecessor Nigel Clough, Freeman has previously represented Nottingham Forest, Notts County, Derby County and Mansfield Town.
Kilmarnock also expressed an interest in signing the former Wales under-21 international before parting company with Gary Locke in January.
Meanwhile, United have confirmed they will host Derby County in a pre-season friendly on Wednesday 27 July (kick-off 7.45pm). Wilder’s preparations for the forthcoming campaign will begin at Stocksbridge Park Steels on Saturday 9 July before a visit to Grimsby Town on Saturday 23 July. Both matches kick-off at 3pm. United’s summer fixture schedule concludes with a game against Handsworth Parramore on Friday 29 July (kick-off 7.45pm). That game will take place at the Windsor Food Service Stadium, Worksop.
“We’ve got a good mixture,” Wilder said. “A variety of different tests which is good for us.”