It was City's 13th successive victory in all competitions and restored the Club's five-point lead over nearest rivals Manchester United.
But he insisted no-one was getting carried away despite the Club's record-breaking run of form.
"To win 13 games is good – especially for our fans – but we are only thinking game by game, step by step," said Fernandinho.
"We have now a difficult game in Europe at Napoli and a tough league game at home to Arsenal next Sunday.
"Napoli will not be easy but we know if get a result there it can give us qualification to the next round of the Champions League.
"And we all know how tough the Premier League is. We have to think about each game – everyone can drop points.
"Next week it is Chelsea v Manchester United and one of those teams will have to drop points so we have to try and do our job at home."
Despite dominating territory, possession and chances created, City were given a late score with Albion narrowing the deficit with a 90th minute goal from Matt Phillips.
But Fernandinho said there was little doubt that City deserved to come away with all three points.
"It was a tough game for us – especially in the second half. They made a high press but I think we deserved the win," said Fernandinho.
"We went for the match from the beginning but we conceded some easy goals and gave them a gift near the end.
"But at the end we had lots of options going forward - it was just a shame we could not score more goals as we created so many chances but we won the game which is the most important thing."