His Premier League champions welcome Forest to the Etihad Stadium for a 15:00 (UK) kick-off on Saturday looking to maintain our 100% record.
Grealish has not featured since the August victory over Sheffield United but, having returned to training this week, Guardiola says he could play this weekend.
He also had positive news on Mateo Kovacic, who is edging closer to a return but unlikely to be involved tomorrow.
However, he was less encouraging about Bernardo Silva's fitness.
"Jack is coming back, training well and maybe for some minutes will be ready," he said.
"[Bernardo is] a little injury, not much. I don't know, a week, two weeks."
The Catalan made it clear that he considers City's packed schedule to be the main reason for the current lengthy injury list.
Having won the Treble last season, City are again competing on all fronts in 2023/24 with the addition of the UEFA Super Cup already in this campaign and the FIFA Club World Cup to come in December.
"Less games less injuries," he said.
"A lot of seasons without much rest, this is just that.
"We demand a lot of effort and sometimes they can’t sustain it.
"Jack [Grealish] was at Sheffield United with a knock on his knee, it’s football. Muscular issues are a lot of games."
City beat Forest 6-0 at home last season, with Erling Haaland scoring his second hat-trick in as many games.
Forest manager Steve Cooper described a trip to the Etihad Stadium as 'the toughest game you can play' earlier this week.
Guardiola was grateful to his counterpart for the praise and expects a tough challenge on Saturday.
"It’s a compliment, thank you so much to Steve," he said.
"They were able to do an incredible game at Stamford Bridge and fought a lot v Arsenal and Manchester United, [winning] 0-2 after a few minutes.
"Last season we couldn't win there but they did a good game, missed chances. We can’t deny in the last year at home we feel good. Tomorrow we have to prove it again."
CITY V FOREST APP COVERAGE
Minute-by-minute text updates will begin in our Matchday Centre two hours before kick-off, while our Matchday Live show will begin at 14:00 (UK).
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