The Brazilian was forced off in the first half against West Ham on Tuesday and will undergo an operation in Portugal in a fortnight, but Sir Alex Ferguson hopes the 21-year-old will be fit for the start of the 2010/11 campaign.
"The real bad news we have got is that Anderson has suffered a cruciate knee injury and he’ll be out for rest of the season," confirmed the boss on Thursday. "It’s unfortunate for the boy. It’s a bad blow.
"We’ve assessed the situation, we know he needs an operation. That will be done in two weeks’ time when the swelling has gone down. We’re going to let him go to Portugal to do it. Sometimes we send them to Colorado and to Dr Richard Steadman, but on this occasion he is comfortable with the specialist he has dealt with at Porto in the past. He will deal with it. We made these decisions yesterday once we had assessed the damage. But hopefully, six months, should have him about right for the new season."
The incident itself against West Ham seemed innocuous enough, Anderson stretching to reach the ball to make a pass. "With these types of injuries, it’s usually something simple. He stretched to pass the ball and his knee just popped," added the boss.
"It’s a bad bit of news for him. He was just getting back into the first team after being out for a few weeks. He was looking forward to it and he was showing great energy in the match.
"So that is a blow to us, particularly with the Milan game coming up, because Michael Carrick is suspended for that one."