Kyle Walker will be sweating over his fitness for the World Cup in Qatar after Manchester City confirmed the full-back has had "successful" surgery on a groin injury.
Walker was forced off in the first half of City's derby victory over Manchester United at the Etihad Stadium on Sunday.
No timescale has been put on his potential return but it is understood the club believe he still has a chance of featuring in the World Cup.
A statement from City read: "Kyle Walker has undergone surgery after suffering a groin injury to his left leg during the first half of our 6-3 win over Manchester United on Sunday. The surgery was successful and a more detailed prognosis will be provided in due course."
Walker is still hopeful of being fit for the World Cup - but it will be close. His availability for Qatar depends on how his body reacts to the operation, with the next fortnight key.
Medics working with Walker know he has usually been a "quick healer" from his past injuries.
The player had been feeling a niggle in his groin before the injury worsened in the Manchester derby.
The club have taken the decision to have the operation now, because of Walker's pace and the way he plays and it is not an injury he could manage while still playing.
Gareth Southgate is expected to name his 26-man squad for Qatar 2022 on October 20, which will be well before FIFA's deadline of Sunday November 13.
England face Iran in their opening World Cup group game on November 21 at the Khalifa International Stadium in Doha - the same venue where Germany begin their Qatar 2022 campaign as they face Japan on November 23.
Pep quashes Real clause in Haaland deal reports: 'It's not true'
Pep Guardiola insists there is no release clause in Erling Haaland's contract, saying the Norwegian striker is "settled" and "happy" at Manchester City.
Reports in Spain had suggested there may be a clause in the 22-year-old's contract that would allow him to join Real Madrid in two years' time or for a lower fee than other clubs.
Before Man City's 5-0 win over FC Copenhagen - during which Haaland scored twice, taking his tally for the season to 20 in 14 matches - the club rejected those reports and in his post-match press conference, Guardiola reiterated the club's stance.
"It is not true", the Spaniard said. "He has not got a release clause for Real Madrid or any other team. It is not true, that is all I can say. The rumours, people talk, we cannot control it. Always we must worry about what we can control.
"He adapted really well and I have the feeling that he is incredibly happy here. We will try, with all the people who want to stay here, to make them happy. That is the most important thing.
"In the end, what is going to happen in the future, nobody knows. What is important is that he is settled perfectly here, he is happy and he is incredibly loved by everyone. This is the most important thing."