Manchester United boss Sir Alex Ferguson admits Dimitar Berbatov is struggling to make Sunday's visit to Chelsea.

The 27-year-old suffered a knee injury in Saturday's defeat at Liverpool which ruled him out of last night's 0-0 draw with Villarreal and it seems doubtful he will be available for the weekend either.

"He has a little tweak behind the knee," he said.

"We did not want to take a chance tonight and really it is too early to say for Sunday."