United are keen for the Belgium worldwide to stay but negotiations, which began last season, have dragged on after he rejected an offer in September.
However, Stone also cites the close relationship between the player and manager Jose Mourinho as a possibly deciding factor in whether Fellaini opts to sign a new deal. As the former Everton man is out of contract in the summer and United do no hold any options to trigger an automatic extension he would be free to sign a pre-contract agreement with any club outside the Premier League in January.
Felllaini was the first signing of David Moyes' ill-fated era as Manchester United boss, arriving on a £27m deal in August 2013.
Manchester United have ruled out selling Marouane Fellaini in the upcoming transfer window despite the midfielder rejecting the offer of a new contract, which leaves him free to negotiate with rival clubs from January 1.
Fellaini's decision has shocked the club at a time when the player has never been as highly thought of by the fans or Jose Mourinho.
Fellaini though is rarely a starter when Mourinho can name his first choice starting line-up - he's made only three starts this season.
Pogba is now closing in on a return - and could feature against Newcastle on Saturday - which will limit Fellaini's chances of more starts.