The Belgian superstar has not played since the Champions League clash with Inter Milan on 18 September and has made just four Premier League appearances so far this season.
The 33-year-old is dealing with a thigh problem and Guardiola admits that it has been a slightly confusing rehabilitation for De Bruyne, who is back in training, but still is unsure when he will play again.
'I would like to tell you, especially I would like to know it, but I don't know right now,' Guardiola said when asked for a return date for De Bruyne.
'He feels that he can train, but not to go to that level that we need in competition. When you kick the ball or something, he still has pain and he doesn't feel [right].
'Kevin has to feel good to express his huge talent that he has. He's feeling better, but not the best.'
De Bruyne will certainly not play when the Premier League champions travel to take on Tottenham in the Carabao Cup on Wednesday night, as Guardiola deals with a number of injury headaches.
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'For sure, if these guys don't come back as quick as possible, we'll struggle,' said Guardiola. 'Because we cannot sustain with just 14, 15 players for the season. We need the players to come back.'
The Catalan is expected to throw in some youngsters against Spurs on Wednesday night, although it will not be an entirely youthful side given the strength of the opposition.
'We have a problem that we have a lot of injured players and I cannot play like I would imagine,' he said. 'I don't want to put much pressure on the young players to be in this stage against this opponent, for the way they play. That's why I have to make a mix for the players, for split minutes.'
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