Ferguson said he was going to make "seven changes" from the side which beat Fulham last weekend, but Rio Ferdinand and Michael Carrick were the only regular starters omitted from the staring XI for the encounter with Everton at Old Trafford.
The move paid off as United ran out 2-0 winners thanks to goals from Ryan Giggs and Robin van Persie to move 12 points clear of Roberto Mancini's men, who were beaten 3-1 at St Mary's.
"Yeah it did," he told Sky Sports 1, when asked if Saturday's result had prompted a change of heart.
"I thought I'd make about seven changes, but when I saw the result yesterday [Saturday], I knew how important the game today [Sunday] would be for us and we can make more changes later on in the season."
"We have to win our games anyway, it doesn't matter what happened with City yesterday," he continued. "Thats the way we should look at it, to concentrate on our own game and we will be okay."
Ferguson was full of praise of goalscorer Giggs, whose goal ensured he maintained his own record of scoring in all 23 Premier League seasons.
"His legacy lives on, he is a fantastic human being," Ferguson said. "He's up and down that pitch all day and has shown fantastic energy for the game, it is wonderful to see."
The player himself was more concerned with getting the three points than personal milestones and demanded his side maintain their recent impressive form.
"It was an important goal. The main thing is that it set us off.We had to against a really good Everton team," he said. "The performance wasn't important but I think we played well.
"For us (it is important) to continue our good form and get the results and we will be okay. We have been in really good form lately.
"We have players on our bench who would walk into any other team, the squad at the moment is really strong.
"We have enough experience but you can never take anything for granted and we have to keep playing well. You never know what happens."
Everton boss David Moyes was pragmatic about his side's defeat and refused to be too critical of his charges.
"We didn't start the game very well, Manchester United were very good in the opening period," he said.
"The goal just before half-time made it difficult, but full credit to our lads, we stuck at it.
" We didn't give in and I am a bit disappointed we didn't get the goal in the game."
Next up for United is Wednesday's Champions League clash with Real Madrid, where Ferguson has the chance to pit his wits against Jose Mourinho - who was at Sunday's game - once again.
"I had a chat with him, they had a regret result yesterday," Ferguson said. "It will be a fantastic match on Wednesday.
Giggs added: "It will be a fantastic game. It doesn't come any bigger than playing Real Madrid, we can look forward to that now."