The Spain playmaker struck in the second minute at the Etihad Stadium and added a sublime chip 21 minutes from time as City moved within four points of Barclays Premier League leaders Manchester United.
Silva could have had a hat-trick but rolled a shot narrowly wide of the far post just moments after scoring his second.
The 27-year-old had scored only one goal this season prior to the match but Platt feels his performances have still been highly effective.
The first-team coach, said: "Last year he had a few more goals under his belt but we know how important he is whether he is scoring goals or not.
"I think his performances have been right up there. I think it would be harsh to say it has been lacking.
"He is in the team for all sorts of different reasons, not just his goalscoring ability.
"I think his performances of late have deserved goals. I am pleased he got the two and he should have had a third."