Despite naming a much changed side and going into the match on a four-game losing streak, Premier League side Norwich comfortably made it through to the next round.
Indeed the result never looked in doubt once Elliott Bennett fired the Canaries in front after half an hour, Simeon Jackson then doubling the advantage just before the break.
Robert Snodgrass put a gloss on the result in the second half, leaving the majority of the 13,000 sell-out crowd at London Road disappointed.
Speaking after the game a clearly frustrated Ferguson said: "We've got our largest crowd of the season and I have to apologise to my own supporters for that performance because we're at home in a cup game which my players, for whatever reason, turned into a pre-season game.
"I'm quite glad it's taken me a while to talk to the press, and I haven't had a meeting with the players yet, because sometimes you can say things you might end up regretting.
"It was a shocking performance. If you've got your first proper tackle after 65 minutes in a cup tie then you're going to lose.
"I can accept people playing badly but the most disappointing thing for me was Norwich looked like they wanted it more, and they were the ones that made a lot of changes.
"I know what I'm going to say to the players. They'll expect me to pick them up again and perhaps they're starting to take that for granted. When you go on a good run and then you've got a cup match and it's a home tie, you think it could be another step towards improving in the season.
"Now we've seen what we've seen today, and it's the easiest game Norwich will have all season. All of a sudden you're back on the back foot, and you've got to go to a hard game like Forest.
"I gave my players two days off so there's no excuses whatsoever. I'm as frustrated as I've been for a while because I didn't see that performance coming.
"They've definitely let the fans down but I think the players have let me down today and they're going to have to give me a response, simple as that."