Wayne Rooney will be out of action for up to four weeks after injuring his ankle in training on Friday.

The striker will miss Sunday's match against Blackburn Rovers, although the forthcoming international break means he could miss as little as three further games, against Bolton, Sporting Lisbon and Fulham.

Sir Alex is hopeful of having the 22-year-old striker ready for action for the trip to Anfield on 16 December.

A club spokesperson told ManUtd.com: "Wayne Rooney injured his right ankle in training and will be out for about four weeks."

It is even more frustrating considering Rooney's scintillating form since overcoming a fractured metatarsal sustained on the opening day of the season.

He has only just been named Barclays Player of the Month for October, having netted eight goals in his last seven games.

Sir Alex had said earlier on Friday that he wants to use Louis Saha sparingly and from the substitutes' bench, but he will now be forced to call on the Frenchman as Carlos Tevez's regular strike-partner.