Fergie spent £53 million on three players last summer.
He said: "I think we did what we had to do last summer. We brought in a goalkeeper to replace Edwin van der Sar.
"We added that to the decent squad we had - in terms of youth and experience - and so at the start of the season I was confident we had the nucleus of a very good team.
"Then we got hit with injuries, plagued almost, for four months and now it's given me that headache of picking players and not knowing who to leave out.
"There's a good nucleus here, a lot of youth that will get better."