The Spanish winger and Brazilian midfielder both put in full 90 minutes shifts as their new club hammered Newcastle United 4-0 at the Etihad Stadium and their respective performances pleased Pellegrini.
"Both of them are very important players for us. They're different players," the Chilean told Sky Sport.
"Navas always plays wide and he gives a lot of good passes inside the area and Fernandinho works the 90 minutes with the ball and without the ball.
"I'm very happy with both of them for the way they played today."