The Norwegian came off at half-time against Borussia Dortmund with the boss reporting his striker had a slight problem with his foot and a fever.
Haaland has not missed a Premier League game since joining City, but the boss says he doesn’t know whether he will be fit enough to play yet.
“He feels better, but we train this afternoon, and we will assess in these few hours,” said Guardiola.
“We will see how he feels. After we will decide - I will know it in two hours if he can play. “
Guardiola also revealed there are no fresh injury concerns from midweek, adding: “After the game everyone trained well. I have to wait for the people coming back to know exactly how they feel."
The boss also offered encouraging news on two of City’s longer-term absentees.
“They are not ready for Leicester,” Pep confirmed.
“They are better, Kalvin especially.
“Apparently, when he came to Dortmund, he said he feels really well. He started to train with contact with the ball - he has not trained with his team-mates yet, but he feels really well, and we are surprised.
“If he is fit and can play (at the World Cup) he can play, but right now, we don't know.
"They [Walker and Phillips] are optimistic. They are in touch with Gareth [Southgate]. Hopefully they can be ready and get selected."
And the boss also confirmed Ederson is fit enough to start Saturday's game at the King Power Stadium.
He missed Tuesday's 0-0 draw in Dortmund, with Stefan Ortega making his first competitive start for City.
But the boss says the Brazilian is ready to go.