United manager Sir Alex Ferguson was delighted with the win at St. Andrews but quick to praise Steve Bruce's Birmingham City.
"I think we're getting towards top gear," the boss told Setanta Sports. "You could see signs of that today. Some of the movement up front was very good. Rooney, Ronaldo and Tevez are big threats for all our opponents, and the forward line is looking much better now.
"I actually thought Birmingham were by far the better team in the first half, although we did carve out some good chances for ourselves. They played very well and you have to give them full credit. I would say it was the hardest game of the season so far."
Sir Alex later told MUTV he was relieved to keep Birmingham at bay in the early stages and said Bruce's Blues had unsettled his players with their physical attributes.
"They were very aggressive, very quick about the pitch," he said. "They were a real handful for us. Even at 1-0 we were just praying to get through the match. Late on, they kept pumping balls into the box but we coped with that well. They're a big side, very athletic, and we had to be on our toes in the second half. It's a good result for us, a very good result.
"We only scored once but we were away from home and you have to give Birmingham credit. Ronaldo's goal might have come from a mistake by one of their players but his composure in beating the mean, beating the goalkeeper and then putting it into the net was excellent. He was sensational today. The boy is so good it's frightening. His capabilities are unending."