United were two goals down at half-time after careless errors by Patrice Evra and Nemanja Vidic gave away two penalties but a Wayne Rooney hat-trick and a goal from Javier Hernandez gave the visitors a 4-2 win that edged them closer to a record 19th title.
"I think we played like champions today," Ferguson told Sky Sports. "We kept our heads up and didn't lose faith in our ability and that was a great, great boost.
"We dominated that second half and it was a real championship performance as far as I'm concerned."
"He could have been sent off," said Ferguson. "I thought he got maybe a lucky break. It would have been harsh but he could have been sent off for it."
"We had a strong bench today," said Ferguson who had goal poacher Michael Owen and Brazilian midfielder Anderson among his unused substitutes and only used winger Nani late on with next week's Champions League quarter-final first leg at Chelsea looming.
"I just felt we had to go for it. I brought on Chicharito (Hernandez), put Ryan to left-back, at that point I said to myself goal difference doesn't matter here. Let's get something out of it and we managed to change the game round."
Rooney, who scored an excellent curling free-kick, low drive and spot kick to notch a hat-trick in the space of 14 minutes, agreed the changes made the difference. "I think the substitutions were good substitutions and that's what won us the game," he told Sky Sports.
"Even when we've not been playing well we've been grinding out results so hopefully now with seven games to go we can keep doing that," said Giggs.
