Manchester City boss Pep Guardiola appeared to rule out Jose Mourinho's side last month from a five-horse race but United have since won back-to-back league games to get within four points of fourth-placed Tottenham.
Victory for United, who came back from 2-0 down to win the corresponding fixture last season at the Etihad, will see them move within six points of Guardiola's side ahead of the international break.
"We don't know that. For sure it is an important game, like any other one because we are playing for three points," Silva said, when asked whether the match was their most important of the season.
"We want to win every time we play in the Premier League or any competition.
"It's just three points but for the fans, it means a little bit more because it is a derby and against a contender.
"So if we win we are not only winning three points but we are taking three points from them as well."