Ferguson could not believe what he was seeing as City pulled two goals back and then had a handball claim against Phil Jones turned down by referee Chris Foy.
"It was ridiculous," said Ferguson. "We got careless and made City better than they were.
"They went defensive in the second half and waited for us to make mistakes - and we made them.
"Fortunately we scrambled away with a victory. From a position where we should have battered them."