After being led to believe Fabregas was interested in returning to the Barclays Premier League, United executive vice-chairman Ed Woodward suffered a nasty shock on Thursday when the former Arsenal skipper declared he was happy at Barcelona.
This prompted an immediate response from United, stating their respect for Fabregas' position, which did not quite amount to confirmation they were backing off but given the latest development leaves little room for manoeuvre.
Instead, Moyes must search for alternatives, knowing he has less than four weeks before the transfer window shuts and only eight days before the Red Devils begin their Premier League title defence at Swansea.
Given Moyes has already stated his central midfield resources are below strength, the most obvious course of action would be to push through a deal for Fellaini given his obvious knowledge of the player and a desire from both sides to resume a partnership that proved so successful at Everton.
Yet even that may fail to appease supporters growing anxious at the lack of fresh blood so deep into the summer business.
United do have until September 2 to conclude any deals, yet alternatives to Fabregas are not immediately obvious.
Real Madrid's Luka Modric has been mentioned but the Croat is more in the Michael Carrick mould of a neat passer and skilful ball-player than that of Fabregas, who combines superb ability in possession with a physical presence.
Newcastle's Yohan Cabaye is another but he clearly does not have the former Arsenal skipper's vast experience, and is untested at the highest level.
Repeatedly this summer, Moyes has spoken of the difficulty in securing new players quickly due to the upheaval created by Sir Alex Ferguson's departure.