The move paid dividends as first-half goals from Ryan Giggs and Robin van Persie proved enough to see off a dogged Everton outfit 2-0 at Old Trafford.
United are now 12 points clear at the top of the Premier League and even though it may take some of the edge from his players ahead of Wednesday's mouthwatering Champions League duel with Real Madrid, Ferguson believes it was worth the U-turn.
"As soon as I saw the result at Southampton I thought this was an opportunity for us to get a real comfortable lead," said Ferguson. "I scrapped the changes I originally planned to make.
"I was going to make about seven changes but it was about being realistic.
"We knew if we could get a result then it put us in a fantastic position and we can make changes later on in the season."
That pre-supposes United do make it past Real, whose manager Jose Mourinho met Ferguson ahead of Sunday's game and watched on from the directors' box.
However, after losing the title to City last term, there has been a keen desire for the Red Devils to regain their superiority.
And Everton boss David Moyes is not alone in believing that is what will happen.
"I think 12 points against a club like Manchester United is a big gap to make up," said Moyes. "Football doesn't always go the way it is meant to be but it looks a lot. To be that amount of points ahead is a big thing at this time of the season."