Ferguson said there is no long-term damage with Ferdinand's injury but he was in need of a prolonged rest, meaning both he and Evra will miss Wednesday's match with Wigan and also Saturday's encounter away at Bolton.
"Rio has been to a specialist and there are no major problems with his back, but he won't be involved against Wigan," added the Scot.
"We are giving him a series of exercises, but he should be ok and we hope he'll be back for the Spurs game."
Frenchman Evra is also likely to miss the Carling Cup second leg against Derby later this month, the FA Cup fourth round clash with Tottenham and Premier League matches against West Brom and Everton.
Both players have helped United keep the Premier League's best defence this season, with just 10 goals conceded in 19 league games.
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