The midfielder damaged his thigh while with Spain but is expected to be fit for the derby, along with captain Vincent Kompany, though both will miss the trip to Stoke on Saturday
The Spain international suffered a thigh injury while away on international duty last week and has been ruled out of Saturday's trip to Stoke City.
However, Pellegrini has confirmed that Silva could play a part in the Chilean's first Manchester derby at the Etihad Stadium on September 22.
|6/1||Stoke City and Manchester City are 6/1 with bet365 to draw 1-1 on Saturday
"We will try for the derby - if he’s 100 per cent he can play in that game."
Micah Richards (hamstring), Gael Clichy (knock), Martin Demichelis (knee) and captain Vincent Kompany (groin) will also not travel to the Britannia Stadium.
Kompany, however, is also likely to return for the clash with David Moyes' side, following the injury he suffered in his City's first game of the season against Newcastle United.
"Vincent Kompany is OK but it’s too much of a risk for him to play [against Stoke]," he continued.
"[In] two or three more days he will be 100 per cent."
City open their Champions League campaign in midweek against Viktoria Plzen, before facing their local rivals, but Pellegrini is not concerned by the busy schedule.
He added: "It's a big test for all of the big clubs, all of them are playing the Champions League and Europa League – we have seven games in 21 days.
"It's the same thing October, November, December - that’s why we have 23, 24 top-class players – we will try to do our best performance in every game we play."