Grealish has not played for the Citizens since making a 17-minute cameo appearance as a substitute in a last-gasp 2-1 win at Wolverhampton Wanderers on October 20.
The 29-year-old has since missed City's last five matches, with Guardiola's men suffering defeat in each of their last three games across different competitions against Tottenham Hotspur, Bournemouth and Sporting Lisbon, losing 4-1 to the latter on Tuesday in the Champions League.
Grealish is understood to be nursing a groin injury and the expectation was that he would not be fit to return to first-team action until after the international break.
However, Citizens supporters were surprised to learn that Grealish had been included in Lee Carsley's England squad for UEFA Nations League fixtures against Greece on November 14 and against the Republic of Ireland three days later.
Grealish confusion remains as Carsley, Guardiola offer separate updates
Carsley provided an update on Grealish's situation at his England press conference on Thursday shortly after his squad was announced, telling reporters: "Jack's been training at City for the last couple of days, so we're hoping that we'll assess him when he comes into camp."
He added: "Jack is in the same position as maybe four or five other players that there's question marks over whether they're going to be involved or not... We try and give them as long as we can."
The confusion surrounding Grealish has since been bluntly addressed by Guardiola, who was not in the mood to go into detail about the attacker's situation during his pre-match press conference on Friday that lasted a shade over three minutes.
Asked to share his thoughts on Carsley selecting Grealish for England, Guardiola said: "It's a question for the manager from [England]".
Guardiola was then asked if Grealish will be fit to play for Man City in Saturday's Premier League clash with Brighton & Hove Albion at the Amex Stadium, and he simply replied: "No."
Who else is injured for Man City? Who could be involved against Brighton?
Grealish is not the only Man City star who remains sidelined, as Guardiola has revealed that there is "no good news" on the injury front ahead of their trip to Brighton.
"[There is] no good news," said the Catalan coach. "We have the same [players available] as we did for Lisbon. The players that travelled, still they are there."
Man City will therefore be without defensive duo Ruben Dias and John Stones, who are carrying unspecified problems, as well as long-term absentees Rodri (ACL) and Oscar Bobb (leg fracture).
On a positive note, there were no fresh injuries picked up from Man City's midweek loss to Sporting, with Jeremy Doku, Savinho and Manuel Akanji among those who got minutes under their belts having previously been nursing problems.
All three will be in contention to play against Brighton and the same can be said for Kevin De Bruyne, who made his first Man City appearance against Sporting after a nine-game injury layoff, coming on for the final seven minutes plus stoppage time.
Man City currently sit second in the Premier League table and could return to the summit with a win over eighth-placed Brighton, albeit for only a couple of hours if current leaders Liverpool beat Aston Villa on Saturday evening.