Neville missed the final two months of last season after undergoing ankle surgery but was expected to be fit for the new campaign.
Instead, the long-serving England full-back has been a frustrated spectator as United have stumbled into the new campaign with successive draws.
Neville will miss out again on Sunday afternoon as United face City in the first Manchester derby of the new campaign, with Ferguson revealing the 32-year-old is now recovering from a calf strain.
Ferguson feels it will be at least a fortnight before Neville is fit again, which rules him out of the forthcoming Premier League fixtures against Tottenham and Sunderland and, in all probability, England's Euro 2008 double-header against Israel and Russia in September.
The Scot explained: "It will be another couple of weeks.
"We are frustrated with the situation because the operation was fine.
"The surgeons did find a few little bits in there which they had to repair as well, which meant a longer recovery period but then Gary suffered a little setback with a calf injury.
"That sometimes happens when you are trying to compensate after an operation. So the ankle is okay, now the calf is the problem."
Meanwhile, Ferguson restated his belief Wayne Rooney should be back in action within 'eight or nine weeks'.
Rooney is currently in plaster after suffering a hairline fracture of the foot in Sunday's opening-day draw at Reading.
The England star is resigned to missing up to 12 key games for club and country, including the start of United's Champions League campaign.
However, Ferguson confirmed the injury does not appear to be as serious as Rooney's previous two broken metatarsals and is optimistic about the 21-year-old's recovery time.
"It is only a hairline bit with any kind of fracture, you have to make sure it is dealt with properly.
"It is always difficult to be accurate because everyone is different. I think he should be back playing in eight or nine weeks."
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