McTominay has been linked with the Old Trafford exit and Antonio Conte's Napoli are wanting to bring the Scotland international in for the campaign.
McTominay has just one year remaining on his contract with United, although the club has the option to extend it for a further 12 months.
The 27-year-old is a product of United's academy and has made over 250 appearances for the club since making his debut in April 2017.
Fulham had showed concrete interest in signing the Scottish international over the past few days, and it's thought they were near to completing a deal to bring the midfielder to Craven Cottage on a full-time basis.
But a move looks to be off after Fulham wrapped-up the signing of £25m-rated Sander Berge from Burnley.
This puts the Italian side in pole position to sign McTominay, but United are standing firm on a selling the midfielder, rather than a loaning him for a season.
He also enjoyed his best-ever goal return for the Red Devils last season, scoring 10 times.
Another name bound for an Old Trafford exit is Facundo Pellistri.
The Uruguayan winger is set to join Greek Super League team, Panathinaikos, in a deal worth £5.1million.
McTominay has just one year remaining on his contract with United, although the club has the option to extend it for a further 12 month
The deal for Pellistri would include a sell-on clause believed to be around 40 per cent.
Pellistri was bought from Uruguayan club Penarol for £9m in 2020, but has only started four times for United. The midfielder has spent three spells on loan in Spain, since.