Sinclair is available for around £2m, while Boro want to recoup the majority of the £5m they paid Sunderland for McNair last summer.
Apparently the versatility of the latter is what really appeals to Blades manager Chris Wilder. McNair is generally considered to be a centre-back, but can also play in midfield.
Wilder is ready to start signing players following the summer break. His side are preparing for their first season in the Premier League in 12 years.
Yet is this pair really who Wilder is after?
Do Sheffield United need Sinclair and McNair?
The Sheffield Star reports that the Blades are targeting five new players after their promotion from the Championship.
The first is a goalkeeper, which is expected to be Manchester United’s Dean Henderson returning on loan. They also want wing-back cover for Enda Stevens, an attacking midfielder and two strikers.
Sinclair could arguably fill the number ten role and has done on occasions for the Hoops. Yet the 30-year-old’s preferred position is as a left winger.
Assuming Wilder is going to stick with the 3-4-1-2 formation that has served him so well, this wouldn’t accommodate Sinclair.
Not only that, but the attacker has played in the top flight of English football before. Sinclair was relegated with Aston Villa in 2016 after failing to break through at Manchester City.
His only real success was with Swansea City between 2010 and 2012.
As for McNair, his positions are also not being targeted it seems. However, the 24-year-old would more obviously fit in.
Wilder has limited options in central midfield following the release of Paul Coutts. McNair’s ability to play in defence could also be a valuable asset.
Plus he does have experience of the division from his time at Old Trafford and the Stadium Of Light.