London, Jan. 25 : Manchester United is worried Wayne Rooney's fitness could add to the injury crisis that is threatening their season.

According to News of the World, Rooney is making slow progress recovering from a hamstring injury and United are reluctant to push him back into action too soon.

And as they enter the critical stage of the season, United fear they could be without Rooney for another month. It was believed he would miss three weeks when he limped off on January 14.

Coach Alex Ferguson wants to keep him out until the end of February rather than risk him breaking down. (ANI)