Nugent joined Derby County from Middlesbrough in January, 2017 for £2.5m and has a year left on his Rams contract.
He has scored 15 goals in 54 league appearances for Derby and the 33-year-old could be the man Chris Wilder turns his attention to if Ipswich reject the bid for Waghorn.
The Blades could face a familiar foe in the opening game of the season as opponents Swansea are said to be eyeing a move for Sheffield Wednesday’s Argentinian forward Fernando Forestieri, 28.
Sunderland are waiting to see if the Blades do strengthen their attacking options before considering a move for Billy Sharp.
The Black Cats remain interested in Bradford City striker Charlie Wyke, despite him taking a knock in a pre-season friendly which is set to rule him out of the start of the season.
Bolton remain favourites to land the 25-year-old target man for around £750,000.
Manchester United manager Jose Mourinho has set his sights on former Blades and Hull City central defender Harry Maguire, England’s outstanding player at the World Cup.
The Old Trafford chief hopes a £65m bid will persuade Leicester City to sell the 25-year-old.
Hull City are hoping that Brighton’s Oliver Norwood rejects a £1.5m move to Fulham, where he was on loan last season, and joins their midfield instead.
Valencia are reported to be lining up an £8m bid for Leeds United striker Samuel Saiz, 27, who signed last summer from Huesca for £3m.
Iceland and Maccabi Tel Aviv striker Vidar Orn Kjartansson remains on Middlesbrough’s wanted list, though West Brom and QPR remain interested.