Grealish had to be substituted after 21 minutes of our Champions League clash with FC Copenhagen, and Bernardo was also replaced later in the game after sustaining a painful knock at the top of his foot.
The boss also gave updates on Sergio Gomez and Mateo Kovacic.
“Jack I think will not be ready,” said Guardiola.
“I don’t know [his condition]. I need to speak with the doctors. I only know he is not able to play tomorrow.
“Bernardo we will assess today in the afternoon training session.
“Kova is training and Sergio as well. The rest we will see.”
Guardiola says he is expecting nothing less than a stern test from an improving Chelsea side.
Mauricio Pochettino’s side held the Blues to a 4-4 draw in a pulsating encounter at Stamford Bridge earlier this season.
And the City boss believes his team will need to be at their very best to continue a winning run that currently stands at 11 games.
“They are an exceptional team in all departments,” he said.
“It is one of the toughest games we have until the end of season. They are playing really good. The last games were really good.
“They have everything.”
