Manchester City will be without key midfielder Rodri for Saturday's Premier League clash with Everton.
The Ballon d'Or winner limped out of City's victory over Brentford in their last match before the international break after just 21 minutes with a thigh injury.
It is the latest setback to have been suffered by the Spaniard, who missed most of last season following knee surgery.
He has completed the full 90 minutes for City on just two occasions this term.
Manager Pep Guardiola said at a news conference: "He is not ready for tomorrow."
Asked how long the 29-year-old could be out for, Guardiola said: "I don't know."
Jack Grealish, who has made a big impression since joining Everton on loan from City, is not permitted to face his parent club at the Etihad Stadium this weekend.
The England international appears to have been rejuvenated by the move having fallen down the pecking order at City over the past two seasons.
"The impact has been massive since day one," admitted Guardiola when asked about Grealish's form. "He's started playing minutes and minutes and this is what he wanted.
"The pre-season we had with him - and he's a lovely guy - but for different reasons he didn't play much minutes. He's back to real business, he's playing every game."
Guardiola has not spoken to Grealish since he completed his switch to the Toffees in August.
"Hopefully tomorrow, if he comes to Etihad, we can see him," the Spaniard said.
Guardiola teased that he would have liked to see Grealish play in the game.
He said: "It's the rules. If I become a CEO or president running a big institution in England maybe I would change it.
"If they would play, it would be nice. If they don't play, it's because of the rules. To be honest, I don't have an opinion."
Former City performance analyst Carles Planchart said recently he feels Guardiola needs a break to "regenerate" after more than nine years at City.
Guardiola said: "He's right -- but in 2035, I will start to think about it!"
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Guardiola is determined to lead City back to the top after their four-year reign as champions was ended by Liverpool during an underwhelming 2024-25 season.
He said: "We want to arrive in the last stages of the competitions being close. This is the target I have.
"I see things that we are doing much, much, much better than last season. In every game, we are a little bit better and better. That may give me the energy.
"That is not the job done, it's completely unfinished business, and that's why I'm here."