Manchester City manager Pep Guardiola fears Sergio Aguero could miss the first two months of the Premier League season.
Aguero suffered a knee injury against Burnley on 22 June.
It kept the Argentine out of the final 10 games of City's domestic campaign as well their two Champions League matches in August.
Guardiola says he is now uncertain whether City's 32-year-old record goalscorer will be fit until November.
"We knew the injury was difficult," said Guardiola.
"He still hasn't had one training session with us and Sergio is not a guy who regains his physical condition quickly.