The England international says the result will shock the Red Devils into action.
"We have got a rude awakening," Ferdinand said.
"None of us has been taking anything for granted but subconsciously there may have been complacency.
"Losing any game is disappointing but losing to a team who we have such a big rivalry with is even worse. And the scoreline takes it beyond that.
"It is very hard to take.
"It would be nice if there was a game around the corner," he added.
"But results like this can be turned into a positive. Any complacency that was there will have torn out of us.
"At least we are still a good position even if it doesn't soften the blow.
"Now we have to dust ourselves down and get our minds right for the game at Fulham next week, when we will hopefully get ourselves back on track."