Pep Guardiola claims Manchester City could be facing an "emergency" as injuries, illness and suspensions cut into his squad.
The Premier League champions have been without midfielders Kevin De Bruyne, Jack Grealish and Phil Foden for recent games due to coronavirus, in the Belgian's case, and knocks for the England pair.
De Bruyne is now out of isolation, but Wednesday's trip to Aston Villa will likely come too soon, while Grealish and Foden are still to prove their fitness.
To add to the issues, defender Aymeric Laporte will miss the game after collecting his fifth booking of the season against West Ham on Sunday.
Manager Guardiola, whose side trail leaders Chelsea by a point, says he can ill afford any more problems heading into a difficult December.
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The Spaniard said: "We are in an emergency for the intensity of the squad. We have few people.
"I never complain, I never miss the players who cannot play for any reason and I trust a lot the players. When one is out, another one comes in.
"But to sustain it in December - the toughest month of the year - the fact is we are in trouble because we have few players.
"We have just 15 or 14 players and we are in a difficult position because a lot of players play a lot of minutes."
Grealish has missed City's last three games after sustaining a knock on international duty earlier this month while Foden has been out for the last two.
The pair will be given fitness tests, meaning Grealish could come into the reckoning to face the club he left in a British record £100m transfer in the summer.
It is unclear yet when De Bruyne will be ready to return. Guardiola said: "Kevin is back but he needs time to be fit.
"People who have had Covid explain that it's draining, tiring and takes time. He is a player who needs to be fit for his top form, or he cannot show it."
'We have to see Grealish at his best now'
Guardiola says Grealish must produce his best in the remainder of the season but has praised the way the club's record signing has settled in at City.
In an interview with the Daily Telegraph published on Tuesday, Grealish admitted he has found playing at City harder than he expected since leaving his boyhood club, having scored two goals in his 15 appearances for the club so far.
Asked if it may take until next season for Grealish to perform at his best, Guardiola said: "I don't think so, we will be in trouble! We have to see it right now, the best of course. We have six or seven months ahead of us.
"Absolutely not, I am not thinking the best of Jack Grealish we will see next season. I want to see it this season!"
Despite wanting more, Guardiola is happy with Grealish's initial impact at the Etihad Stadium.
"I would say he settled perfectly. I think it is easy because he knows many English players here and the other guys are sometimes too much (sic) nice people," Guardiola added.
"It is not a problem, he plays good, he has to finish to settle, to find a real apartment to live in. You always need a little bit of time.
"If you analyse the games [and whether] he played bad. Absolutely not. With the quality he has it is difficult to play bad. But the way we played and the expectations every few days... It is completely different to what he lives at Aston Villa. But he did it incredibly well there.
"The commitment with the club was amazing, going in the second division he could leave [but] to stay there and to be promoted and then stay there in the first division. The second season in the first division was incredible.
"Now he comes back from the international break injured and now hopefully come back step by step to his best form."
Ahead of the trip to Villa, City sit second in the Premier League, one point adrift of league leaders Chelsea, and have qualified for the knockout stages of the Champions League with a game to spare.
Gerrard: Grealish deserves warm welcome
Aston Villa head coach Steven Gerrard has urged Villa supporters to give Grealish a warm reception if their former club captain is fit enough to feature on Wednesday.
"Jack very much deserves a warm welcome. I have no doubt he will get that, this is his club and it will be when his career is over because he was here as a little boy," Gerrard said on Tuesday.
"He came through the academy, the club has benefited a lot from what Jack has given and we very much wish him well in terms of the remainder of his career. But obviously not tomorrow for 90 minutes!
"I can feel what he has been through because I have been there myself when you have that opportunity to move on from your club."
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