Manchester City have been left with just two senior central defenders after club sources told ESPN FC that Aymeric Laporte will be out until 2020 following knee surgery.
Laporte, signed from Athletic Bilbao in January 2018, suffered the injury during Saturday's Premier League 4-0 win against Brighton at the Etihad.
And following surgery to repair cartilage and meniscus damage in Barcelona, sources have told ESPN FC that the player will be out until the New Year, although no specific timescale has been put on the 25-year-old's likely return to action.
With former captain Vincent Kompany leaving City at the end of last season to become player-manager at Anderlecht, Pep Guardiola had been keen to add to his defensive options during the summer.
But City refused to match Leicester's asking price for Harry Maguire, who eventually became the world's most expensive defender with an £80 million move to Manchester United, and Guardiola went into the campaign without recruiting a replacement for Kompany.
Guardiola will consider using Brazilian midfielder Fernandinho as an emergency centre-back, with 18-year-old defender Eric Garcia the only other option on City's books.
Tosin Adarabioyo, the highly rated 21-year-old, is on loan at Championship club Blackburn Rovers, with City not having the option cut short his move to Ewood Park.
Laporte had been in line for his first France cap after receiving a call up for the upcoming Euro 2020 qualifiers against Albania and Andorra but had to pull out following the injury.