Manchester United yesterday took their biggest lead at the top of the Premier League in 12 years with a 2-0 victory over Everton that takes them 12 points clear of the champions Manchester City with 12 games left to play.
With the Real Madrid manager, Jose Mourinho, in the stands before Wednesday's Champions League last 16 first leg at the Bernabeu, Ferguson said that he had changed his team to take advantage of City's 3-1 defeat to Southampton on Saturday.
He said: "I was going to make seven changes, then, when I got the result, I thought this would be a more important game for us.
"It would give us a comfortable lead and we could make changes later on in the season. Realistically, we knew if we got a result it would put us in a fantastic position.
"We have to win our games anyway – it doesn't matter what happened to City on Saturday. That is the way we should look at it. I've said it for weeks – concentrate on our own game and we'll be OK."
Not since they were 16 points clear of second-place Arsenal in February 2001, finally going on to win the title that season by 10 points, have United enjoyed such a big lead at the top of the Premier League. Before the game, Mourinho said that Wednesday's match in Madrid was "the game that the world was waiting for".
Mourinho said: "The world is not waiting for other matches in the Champions League, so I hope we can give the world what they are waiting for.
"We already know the position where we will finish [in the league]. Of course I want to win matches. I feel the responsibility of that by managing a club like Real Madrid, but at the same I could think more about the match on Wednesday [when picking his team that beat Seville 4-1 in La Liga on Saturday night].
"I had some boys who played 90 minutes last Wednesday for their national teams and I could give them a rest, but it is such a big match on Wednesday that everyone wants to play, no one will be tired."
Robin van Persie and Ryan Giggs scored for United, with the latter at the age of 39 now having scored in 23 consecutive league seasons for his club. Ferguson said: "I think all the superlatives have been used and he doesn't need any because his legacy lives on.
"He's just a fantastic human being. In this game again, at 38 years of age, or is he 39? Maybe 40! I don't know, but he's up and down that pitch all day and showing fantastic energy for the game. It's wonderful to see."
Ferguson had warned in his programme notes that if his players were to throw away a lead as they did in the corresponding fixture last season when Everton scored two late goals to snatch a 4-4 draw, they would "feel the full effect of the hairdryer!"
He said after the game: "I thought they [Everton] dominated in the first half for 20 minutes in terms of possession and had a couple of near things – they were always a threat from corners and have great delivery from [Leighton] Baines.
"We saw that through and played much better in the second half without scoring the goals. We were really in control. They must remember what we call a bad experience [last season's 4-4 draw] and that was one last year. So when it came to that last 15 minutes they showed a really steely determination to make sure nothing happened silly."
Ferguson said that Phil Jones and Jonny Evans were both minor doubts for Wednesday's game, with the former having to come off with an injury yesterday. On the title race, Ferguson said: "Look at the next game and win the next game. That is the only thing we can do, then win the next game. That is all we should think about."