Pep Guardiola has revealed that Benjamin Mendy missed Manchester City's Premier League victory against Fulham because of a knee problem and he does not know how long the French defender will be out.
The left-back missed much of last season with a knee ligament injury sustained against Crystal Palace last September.
He returned to action in April, in time to make France's squad for their World Cup-winning campaign in Russia, where he played once, in the final group match against Denmark in Moscow.
But Guardiola revealed that Mendy, 24, missed Saturday's 3-0 win at the Etihad with a knee problem.
"I don't know how many days he will be out," said the Spaniard, whose side play Lyon in the Champions League on Wednesday.
Guardiola said Mendy could be missing for "weeks or days and maybe longer," according to the Metro newspaper.
The manager is demanding improvement from City despite the victory against Fulham that keeps them on the coat-tails of Premier League pacesetters Chelsea and Liverpool.
The City boss's frustration was evident throughout the game as he showed his irritation on the touchline with what he saw as sloppy play.
"When a guy has a simple ball but they make an extra pass, an extra dodge and they miss the pass, I'm angry, I'm upset with my players," said Guardiola. "They know that, we spoke many times.
"If they miss the goals or assists, I don't care. If they are dribbling and lose the dribbling it doesn't matter."