Dias left Benfica for City earlier this month.
And ahead of tonight's Champions League group opener, Dias said: "I won't say it is more of a game, more of an opponent, I am focused on winning and being better, nothing more than that.
"There was no rivalry between Rúben and FC Porto. They are a strong team, they know very well what they do on the pitch, very strong at the dead ball and in the transitions. Everyone here is aware that it will be very difficult and the team has to be very strong.
"The pressure here is greater. At Benfica we always play to win and here the idea is the same. Context is different, level too and, of course, the pressure turns out to be very high. But that's what I also came in for. All this time I've been preparing to face this as strongly as possible."