Silva has not played for City since suffering a thigh injury while on international duty with Spain in August.
And, after Tuesday's 5-0 win over Wigan Athletic in the League Cup, Pellegrini confirmed that the midfielder was unlikely to feature in the Premier League game against Aston Villa on Saturday.
"We'll see if David is fit in the next day," Pellegrini said on Tuesday.
"The doctor understands better than me what happened – I think maybe for next Saturday I don't think he can play but maybe for next Wednesday against Bayern, he could be fit."
The City boss made 10 changes from the 4-1 win over Manchester United on Sunday for the visit of Wigan, with Micah Richards and Gael Clichy both making their returns from injury.
Pellegrini was pleased to be able to give both players a full 90 minutes.
"It was not easy for Micah because he hasn’t played since Bayern Munich in pre-season, it's a long time but I think he did really well because it’s not easy to be out for so long," he continued.
"This match was very important for him and for Clichy, who both came back. It was a useful match for the team."