The England number one did not feature in the Capital One Cup fourth-round tie at Newcastle in midweek but it remains to be seen whether his costly error against Chelsea last weekend will lead to him forfeiting his place in the Blues' Barclays Premier League line-up as well.
Asked if Hart would play against Norwich, the Chilean said: "Tomorrow you will know the answer."
Various commentators have had their say on Hart's form and Pellegrini must decide whether dropping him will protect him from the limelight or further knock his confidence.
Asked whether it was a difficult decision, he added: "It is a decision I have to take every week with 22 players of the team."
Costel Pantilimon played ahead of Hart on Wednesday night and the Blues boss would not be drawn on how the Englishman had reacted to that decision.
"You must ask Joe - I can't answer for him how disappointed he was," Pellegrini said.
"All of you and the players and me all saw what happened. But he is a football player and every week he is under the same pressure.
"I am always careful with all the players, not only Joe."
The error against Chelsea, which led to the London outfit's winner in their 2-1 league victory at Stamford Bridge last Sunday, was the latest in a series of high-profile blunders made by Hart for club and country.
Romania stopper Pantilimon, who has become City's regular goalkeeper for domestic cup competitions since joining them in the summer of 2011, was fairly impressive in the 2-0 extra-time win over Newcastle but if he were selected to start on Saturday, it would be his first Premier League appearance.
What is certain about City's team for the Norwich contest is that it will not feature Stevan Jovetic, Javi Garcia - who both picked up injuries in the Newcastle game - or Vincent Kompany.
Blues skipper Kompany has missed the last four games due to a thigh problem and, regarding the Belgium defender, Pellegrini said: "Vincent is progressing but I think it will be after the international break maybe that he will be fit - before that I think is difficult.
"He is a very important player but I think we have a strong squad just for this case. Other players can play.
"We played the last five matches (Kompany's last appearance was when he came off in the first half of the victory over Everton on October 5), won four and lost just one against Chelsea, and I think we deserved more.
"So he is always an important player, but I think we can play also without him."