But the United gaffer admits he was surprised by the scoreline at Old Trafford on Saturday.
Cristiano Ronaldo scored two goals while Dimitar Berbatov, Michael Carrick and Danny Welbeck scored one each.
“It was a surprising result because the first half performance was very disappointing,” Ferguson told Sky Sports.
“I think maybe getting the early goal relaxed us too much because we did not play with our usual sharpness and speed.
“I think we were a bit fortunate to be 2-0 up at half-time, but the second half was fantastic.
“They kept their discipline and made it hard work for us. We handled their throw-ins very well too.”
Ronaldo scored his 100th goal for the club in the game.
Ferguson said: “He was very pleased and the crowd was delighted. He is on fire now, he’s back.
“He has overcome his operation and he’s getting quicker every game.”
Fergie was also delighted with the stunning goal by Danny Welbeck in his Premier League debut.
“Unbelievable,” said the United boss. “To score on your full debut with a goal like that, he will remember it for a long time.”
He added: “I think it is a difficult league, you can drop points anywhere,”
“But we have got to motor on and make sure that we get to within a couple of points of the leaders by the New Year.
“If we do that we’ve got a chance.”
