"It was a very tight game, playing against a world-class team," the former Arsenal captain told Sky Sports 1.
"We knew it was going to be difficult. The 2-0 was a great result over there. It's never easy to go to Manchester and win the way we did it.
"Apparently, there was a penalty not awarded and the goal from Neymar in the first half was onside. But we take a lot of positives.
"I think we played a lot better than the last few games. We were not at our best and today is a way to lift the spirit of the team.
"We go home happy. For the last couple of games, we could not have said that because we were not happy going back home after some negative results.
"I think we played a good game today against a class team and we are proud of it."