Benitez would not be drawn on the nature of his relationship with Ferguson.
"I am a manager and I just concentrate on doing my job," he said, before adding that he will not be joining his United counterpart for a glass of red wine post-match.
"We know that he has a good team so this will be a very difficult game. That is normal. When you're running a top side and you're playing against top sides, it's always difficult."