Manchester City manager Pep Guardiola fears striker 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. He has been out for a long time, so maybe in one or two months he will be ready."
Aguero's obvious replacement, Gabriel Jesus, scored five goals in 12 games at the end of last season.
Guardiola does have new signing Ferran Torres available for Monday's trip to Wolves. However, Torres is more of a wide player, so the likely alternative to Jesus would be Raheem Sterling, deployed in a 'false nine' role.
With veteran midfielder David Silva leaving City for Real Sociedad during the summer, it leaves Guardiola heading into the new campaign without the remaining stalwarts of his club's first title-winning squad from 2012.