Wayne Rooney looks set to miss the Manchester derby on 10 November after Sir Alex Ferguson said the striker's ankle injury could keep him out of action for longer than estimated.

The Manchester United striker, who last week signed a new five-year contract, is currently recuperating in Dubai after suffering the injury in training. When asked this morning whether he still thought the injury would sideline the striker for no more than three weeks, Ferguson said: "I think it may be longer."

Rooney insisted earlier this month that, despite his ankle being used by Ferguson as a reason for leaving him out of the team, it had in fact given him no problems all season. But last week, during an extraordinary few days that ended with him committing his future to the club after previously stating a desire to leave, he did indeed injure the joint in training. Ferguson told the local radio station Key103 at the time that he "will be out for three weeks".

Ferguson said today: "There is no recovery, it is just rest. Before he went away we did his remedial in terms of what we could do at the time. Thereafter, rest – we're quite happy with that."

Rooney has struggled for form this season, scoring only once for United. But his absence has reduced United's frontline options, with Michael Owen also facing an extended spell on the sidelines. Owen was hoping to return from a groin strain in the midweek Carling Cup tie against Wolves but pulled a hamstring in training.

Ferguson said: "It is disappointing for him. It should be four or five weeks. The last thing he needs is a hamstring injury. It is a loss because with Wayne being injured it only gives us the three options at the moment."

In their place, Javier Hernández has impressed with four goals in four games while Dimitar Berbatov shone in the opening weeks of the campaign. Federico Macheda is Ferguson's other forward alternative.

The veteran midfielder Ryan Giggs is set to return to training on Monday after a fortnight out with a hamstring injury but Owen Hargreaves remains some way off a return. United had hoped the former Bayern Munich midfielder would soon be ready to take a place on the bench after a long battle with knee problems. Ferguson said: "He was making very good progress when he first came back but that seems to have stalled a bit and he is back with the physios now."

Hargreaves, 29, has not started a game since September 2008 and has made only one brief substitute's appearance, towards the end of last season.