"When you get the result, you have to look at the plus points and there were some plus points," Fergie said.
"Nil-nil in the Nou Camp is not a bad result.
"We sealed off the areas where teams don't normally do well against Barcelona. They didn't make a lot of chances.
"Going to Old Trafford at 0-0, we have a marvellous chance.
"On the negative side, we should have done better with possession. We had opportunities to counter-attack but gave the ball away too easily.
"The way they play they always have an extra man in midfield so possession is always going to be in their favour.
"You have to show patience and quality and Barcelona have that, but we had the answers.
"At Old Trafford we have to impose ourselves more and I think we will."