Manchester United boss Sir Alex Ferguson has complete faith in Dimitar Berbatov going into today's showdown with Chelsea. It is obvious the loss of Wayne Rooney causes him a problem ahead of Saturday's top of the table clash with Chelsea.

Yet, in making a single striker his preferred formation, in which Berbatov has no role, Ferguson has given himself an instant replacement.

The Bulgarian cannot be expected to match Rooney's work-rate - few in the United squad could - but the Red Devils spent a club record £30.75million on him for a reason and Ferguson does not expect the former Tottenham striker to let him down in his hour of need.

"I haven't liked leaving Dimitar out - and now he is in," said the United boss, who is aware public perception of Berbatov is not totally favourable.

"The split must be 80-20 in his favour.

"If we sign a big player and he is not scoring 50 goals a season, including 16 overhead kicks, you are always going to get a discerning voice.

"Everyone has their own favourites and supporters have diverse views.

"I used to get a letter from a supporter saying I was off my head because I wasn't playing Steve Bruce at centre forward, although in fairness it was probably Brucie writing it himself or his granny."

Berbatov has produced a couple of battling performances in Rooney's absence lately, which have guided United to crucial victories at Wolves and Bolton.

He is more likely to attack with a sword than a sledgehammer, but Ferguson is confident Chelsea will still feel the same thrust.

"The one thing you cannot dismiss is Dimitar's ability and talent," he said.

"He is a fantastic player.

"He can play on his own up front. What you need is to give him good support."