The Belgian midfielder – a big money buy last summer during David Moyes’ reign – is set to be cut loose after just one disappointing season at Old Trafford.
Louis van Gaal is understood to have deemed him surplus to requirements after pre-season, with a loan move looking the most likely option.
Napoli have already discussed the possibility of drafting in Fellaini for the 2014/15 campaign, but their interest was thought to have ended when United demanded £4m.
The Premier League giants are said to have since dropped their demands by around £500,000, but the Italians are hovering nearer the £1.6m mark.
However both sides are keen, which hints that a compromise may well be reached.
Fellaini was rumoured to have been ready to battle for his place under LVG, yet with the Dutchman having seemingly reached a decision he could look to move on in a bid to revive his career.
A move to Napoli contradicts some reports revolving around Arturo Vidal, as some outlets have suggested he could be sued in a player plus cash deal for the Chilean.
The Naples side will look to Liverpool’s Lucas Leiva should the Fellaini deal collapse again.