Roy Keane believes Sir Alex Ferguson will need to buy another striker when the transfer window reopens in January, if the club are to maintain their domestic and European challenges this season.

Speaking in the wake of Sunday’s 1-0 defeat to Chelsea, Keane fears that United lack the firepower of title rivals Chelsea.

“The biggest disappointment is we didn’t score at Chelsea. Maybe the manager needs to buy a striker in the new year,” Keane told The Sun newspaper.

“We’re a bit short up front and if one or two are injured we could struggle.”

United have been linked with a move for West Ham’s Jermain Defoe and Keane suspects moves to strengthen the squad are already afoot.

“I am sure the manager is already taking care of that, particularly as we are looking to win the Premiership, the FA Cup and the Champions League,” Keane said.

“We know it’s going to be tighter than ever this season.

“And who is to say Chelsea won’t go out and spend even more money in January?”