The Etihad triumph, which saw Sergio Aguero net twice, was our final fixture ahead of the two-week break from domestic fixtures.
City's next run out is a trip to Norwich on Saturday, September 14, and Fernandinho says our victory against the Seagulls leaves us in a strong position.
"We're really pleased," he said.
"We played well today. We scored a lot of goals and conceded a small number of chances.
"I think that’s the best way to go into international duty and get back stronger for Norwich away."
Fernandinho replaced the injured Aymeric Laporte on 37 minutes and, in his first outing of the season, showcased his versatility with a convincing performance alongside Nicolas Otamendi at centre-back.
Fernandinho cut a composed figure at the back, and says City's players are prepared to play in whichever position required.
"It’s not easy [to come on as a substitute], especially in the first half," he explained.
"But every player should be ready to play at the time the manager needs.
"Of course now we pray that Aymeric can recover as soon as possible. We need everybody fit to fight for the title until the end of the season.
"We’ll see how long he will be out for. We don’t know yet but I’m sure John [Stones] will be back soon.
"We’ll be there ready to play wherever the manager needs."