Pep Guardiola has warned that Kevin De Bruyne is not a certain starter as champions Manchester City host Chelsea on Sunday.
De Bruyne, City's star man as they won the Premier League by a record margin last term, is still being eased back into action after missing most of the first half of the season through injury.
The Belgium playmaker appeared only as a late substitute as City returned to the top of the table with a victory at Everton in midweek.
At the time Guardiola admitted he wanted to ensure De Bruyne remained fresh to face his former club at the Etihad Stadium this weekend, but now he has said there are no guarantees.
Speaking at his pre-match press conference, Guardiola said: "It's quite possible (he does not play). Every player knows it's quite possible to play and quite possible not to. It is what it is.
"At the end we judge the players for who they are but they are to perform. There are moments when they are not in better condition, when team-mates are in better condition than them.
"In football what you have done is in the past. You have to do it again."
Guardiola, however, insisted he had no problems with De Bruyne's form and did want to hold him back at Goodison Park.
"We try to control the players," said Guardiola, who caught the eye in a multi-coloured striped jumper.
"He played the last two games. I preferred (he played) for a few minutes at Everton.
"He went out for five mins, plus extra time, and he was incredible – giving the assist, the behaviour, the attitude, everything. I want him to sustain that for a long time.
"Sometimes when you're out a long time injured you need (to be careful) a bit there. I don't want him playing game, game, game."
Guardiola was also asked for his response to remarks from Aleksander Ceferin, president of European governing body UEFA, apparently criticising him for not attending a briefing on the introduction of VAR in the Champions League.
Ceferin felt coaches of all the clubs involved in the competition should have attended the talk on Monday but he said only the managers of Juventus, Lyon, Paris St Germain, Roma and Porto were present.
He accepted Liverpool, who had a game on Monday, could not attend but he said of others: "If they complain about referees they should at least come see what the experts say about VAR. They have no excuses any more – especially the ones who did not come."
Guardiola said the rescheduling of the game against Everton on Wednesday made it difficult for him personally.
He said: "I respect a lot what the president of UEFA said but I don't agree with him, I'm sorry. Brian Kidd (assistant coach) was there. He travelled, he was in the meeting and I have on my table the report.
"The problem was on Wednesday we had a game. The game is more important for me to be with my players. On Monday and Tuesday we had the training sessions.
"I would have travelled, I had the tickets, but the Premier League decided to play between Arsenal and Chelsea the game at Everton."
