Spurs won today's early kickoff 2-0 at the Etihad as Brennan Johnson and Joao Palhinha struck for the visitors.
Dias said afterwards: "Spurs are a team who can be very dangerous, they started the game very well. We didn't react the best way in sticking to our game. The second goal is unfortunate, it cannot happen.
"We chased but there was a lot of things to do better. Not everything was good in our first game and not everything is bad now so we have to get back to work.
"Frustrating, we want to win even more at home in front of our fans in our first home game. It is what it is, it's football we look forward."
On signing a new contract with the club, Dias added: "It says about our ambition, it says that we want to stay here and win trophies and that's the mentality of the club, nothing has changed."