Ferguson saw Real demolish Barcelona 3-1 at the Nou Camp ahead of this week's Champions League second-leg.
"They were fantastic," said Ferguson.
"Every part of their game was spot on. You get that sometimes, I've experienced it myself. You need 11 players to play well but, on an odd occasion, you have 11 players who were absolutely superb. That's what you had the other night.
"I don't think they'll reach that height on Tuesday. I think it was a one-off performance. They'll still play well and we'll have to make sure that we play well.
"We'll be OK because it'll be a different game. Their counter-attacking was terrific. We're aware of that and our preparation has to include that, but I think we'll score, I really do."
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