The Red Devils booked their quarter-final place with a narrow win over QPR at Old Trafford with Carlos Tevez slotting home a penalty 14 minutes from time.
It leaves United still on course for Wembley but with Arsenal, Chelsea and Liverpool among the potential last-eight opponents, Ferguson could be tempted to pick a stronger side for the next round, to be played at the beginning of next month.
But the Scot is adamant he will stick with youngsters such as England Under-19 forward Daniel Welbeck, who was brought down by Peter Ramage for the vital spot-kick.
"I won't be changing," he said.
"I will definitely give players who need games a chance in the next round."
No-one could deny United deserved their success even though they wasted a succession of half-chances and were not as clinical as they might have been given their dominance of possession.
"We deserved it," said Ferguson.
"We played with great energy and speed. It was always going to be tough to get that first goal because QPR's defensive record is good but overall I am pretty pleased."
Tevez will be delighted to get his name on the scoresheet as he aims to prove he is worthy of ousting Dimitar Berbatov or Wayne Rooney from the front-line striking spots.
Welbeck is some way behind in the pecking order but Ferguson feels the youngster is showing real promise.
"Danny is an exceptionally talented young lad," he said.
"He has been troubled by a groin injury recently and only played his first game back at Celtic in a reserve game last week.
"He is probably a bit short in fitness terms but he made a difference when he came on."
For QPR it was a case of what might have been.
Once they went behind they threw caution to the wind and it might have brought them an equaliser, although temporary boss Gareth Ainsworth insisted he had got his tactics right.
"We were a bit cavalier towards the end and might have got a breakthrough, which would have been a fairytale," he said.
"But we got the tactics right.
"Once we pushed three players up front, Manchester United started to create chances. We would not have survived if we had done that all night."
Ainsworth must now get his side ready for Saturday's encounter with Burnley, although he must do so without Gavin Mahon and Lee Cook, who have both suffered knee problems and Daniel Parejo, who was forced off with a back injury.
"They are problems we could do without," said Ainsworth.
"I will be making changes that's for sure.
"We have given a good account of ourselves and this is a fairytale for me.
"But we are back down to earth at Burnley on Saturday.
"The Championship is important for us. We have massive ambition and we want to get out of it."