"I think Wayne Rooney will be out for another five weeks," said Ferguson.
"He'll have to pick up his fitness again. I would think five weeks should be about right."
"We won't be buying in January, definitely not," Ferguson said in the Independent.
"If you want someone to play in Europe, you are limited right away. There are hundreds of players cup-tied.
"You have five months left of the season, I will have Antonio Valencia back hopefully towards the end of February, which is a new player coming back.
"If Michael Owen gets back, it is another new player coming back. So with the squad I've got, I don't see any reason for us to buy anyone."
skysports.
Sir Alex Ferguson has revealed that Wayne Rooney's shock contract U-turn came about as a result of the animosity shown towards him by Manchester United fans.
The England striker looked set to depart United after questioning the club's trophy-winning potential - with Manchester City the most likely destination - but, just two days after confirming his intention to leave, he signed a new long-term contract at Old Trafford.
While cynics have suggested that Rooney's desire to leave was no more than a ploy to increase his wages, Ferguson believes that the 24-year-old changed his mind because of the ire aimed in his direction by the United faithful.
The most drastic example of the supporters' distaste came when a group in hoods issued death threats at his house. "Nobody enjoys that sort of attention," Ferguson said. "When he saw the impact his decision made it took him aback and he had a rethink."
Now that his future is resolved, Ferguson is adamant that Rooney will cast off the slump in form that has affected him ever since the World Cup. The former Everton man, who is currently injured, has one goal in the Premier League this season - and that was from the penalty spot.
"I don't know the reason for his loss of form because it started in the World Cup," Ferguson said. "Whether some clubs have been filling his head in that period to affect him we don't know. The important thing is for us to put it behind us. But certainly something has been troubling him."
Asked if the contract saga was it, he replied: "I think that this has been preying on his mind."
Boss explains Rooney's US trip
Wayne Rooney is heading to America for conditioning work at Nike World HQ in Portland, Oregon.
The United striker's ankle injury has healed but Sir Alex Ferguson and his staff feel Wayne now requires some intensive fitness training to prepare him for match action.
Sir Alex told ManUtd.com on Friday: "The simple reason Wayne’s going to the US is to continue his rehabilitation programme and undergo a week of concentrated training and conditioning under the supervision of our medical and sports science staff.
"We’ve experienced the fantastic facilities at Nike in the past and are happy for him to be there.”
Earlier, Sir Alex's assistant Mike Phelan told reporters at Carrington:
"Wayne will go on Saturday [6 November] and return the following Saturday. If the week goes according to plan then obviously he'll be available when he returns."
This timeline would suggest a possible comeback for Wayne on Saturday 20 November, when the Reds meet Wigan Athletic at Old Trafford.
Sir Alex Ferguson is refusing to rush Wayne Rooney back from the USA despite facing a selection crisis at Old Trafford. The Manchester United boss will have a depleted squad to pick from when his side go to Aston Villa tomorrow lunchtime. Several stars are still struggling to shake off the virus that has swept through his camp this week. To make matters worse, in-form Paul Scholes is suspended after picking up five bookings and Rafael is out with a dead leg. Nani is also battling a sore groin while Patrice Evra suffered an ankle injury in the derby draw. So Rooney’s return to the side would give Fergie a boost. The United boss is already without Owen Hargreaves, Antonio Valencia and Michael Owen, while Ryan Giggs is still out with a hamstring problem. There was speculation United could ask the England striker to fly back in time for the showdown with Gerard Houllier’s men. But despite the growing selection problems facing Fergie, he has told Rooney to complete his week-long training programme at Nike World in Oregon. It means he won’t arrive back in Manchester until tomorrow night. Fergie is more concerned with Rooney getting his head right than rushing him back too soon.
Wayne Rooney's last start for Manchester United came against Bolton in September. Photograph: Brian Snyder/Reuters
Wayne Rooney could make his Manchester United return in Saturday's league fixture with Wigan Athletic at Old Trafford. The striker returned to the club's Carrington training base today to be assessed by the United medical staff after his week-long conditioning work in Portland.
The 25-year-old's ankle injury had healed before his trip but his personal programme in Oregon was designed to catch up on the pre-season conditioning he missed after the World Cup.
"Wayne's had a good week, he's trained very hard, two days two sessions, three days three sessions, we've achieved what we wanted to achieve," Sir Alex Ferguson told the Manchester Evening News.
Rooney's last start for United was against Bolton at the end of September and his only appearance since then was as a substitute four weeks ago. He has missed 13 of United's 20 games this season.
United are waiting for an official decision from the Premier League over the sanction against Ferguson regarding his ban on speaking to the BBC. Reports have suggested the United manager will be fined £65,000 after breaking rules, under the new TV deal, that all managers must participate in pre and post- match interviews with broadcast partners such as the BBC.