Paul Lambert's side earned a 3-2 victory over the Citizens at Villa Park without star striker Christian Benteke, who missed the game due to injury.
Vlaar told The Mirror: "We kept on going. The spirit was really good, we put a lot of energy into it and came back two times from a goal behind.
"It was unbelievable, it was really good. Everybody knows how important Christian is for the team.
"But we showed against Man City we have more to offer and I think we can really be proud of ourselves."
Villa are ninth in the Premier League following the win over City.