The United boss confirmed at his Friday morning press conference that England international defender, Ferdinand, will not be out for as long as he initially feared with the hamstring problem he picked up during last weekend's 2-1 opening win at West Brom.
While he will miss Monday night's visit of Tottenham to Old Trafford, Ferguson is expecting Ferdinand to be fit to face Arsenal next weekend.
However, the Scot also admitted that the injury which forced Vidic off at the Hawthorns is worse than they first anticipated and he is now set to be missing until mid-to-late September.
"Last week we thought Rio's hamstring would have him out for six weeks and with Vidic, we thought it was just a nerve problem. That's reversed itself," said Ferguson.
"Vidic has got a calf muscle injury, which means he'll be four to five weeks. It's longer than we thought. Meanwhile, Rio's injury isn't as bad as we thought and he could be ready for our game against Arsenal. I don't think he'll be ready for Monday. It's amazing how circumstances can change in a few days."