The Red Devils kicked a handful of points clear of Arsenal at the top of the table, scoring three times in the second term to notch their 14th win of the season, and Fergie highlighted veteran Ryan Giggs as the catalyst for the comeback.
"In the first half we were battered. We couldn't handle Charlie Adam. We were terrible,” he told ESPN.
"I don't know the reason for the first half. We were all over the place. Maybe we were too confident.
"We changed at half-time, Ryan Giggs made a tremendous difference. We started to penetrate and I think we were deserved winners in the end."
Ferguson added that he felt his side were always in the contest despite trailing by two goals at the break.
"I know the game's never done in situations like today," he added. "You know at some point we're going to do something.
"You'll get games like tonight. Maybe sometimes we won't come back but we'll always try to come back."