Manchester City manager Pep Guardiola is expecting John Stones to be sidelined "for a while" after he was forced off at half-time in the 3-0 win over Young Boys on Tuesday.
City guaranteed their place in the Champions League knockout rounds with victory over the Swiss champions at the Etihad Stadium, but Stones' injury is a blow with games against Chelsea, Liverpool and Tottenham Hotspur to come in the next month.
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"It's muscular, he will be out for a while," Guardiola told a news conference after the game. "It's a pity for him, he's an incredible professional. It's a pity and bad news for us. I don't know how long."
Stones missed more than two months at the start of the season with a hip injury and Guardiola suggested the England defender has suffered a recurrence of the same problem.
The Spanish coach had better news about Manuel Akanji, who pulled out during the warmup because of a back spasm. Akanji is expected to be fit for the trip to Chelsea on Sunday, while Erling Haaland was able to shake off an ankle injury to score twice against Young Boys.
"I saw the training session, how he moved," said Guardiola. "He felt good, so OK, he's going to play. Now take a rest for Sunday."
Meanwhile, Young Boys coach Raphael Wicky revealed he's planning to speak to captain Mohamed Ali Camera after he was caught swapping shirts with Haaland at half-time.
"I didn't see that, that's news to me and I'm a little bit surprised by that right now," said Wicky. "On the other hand, I don't think it had anything to do with the game or the performance but I'll probably have a word with him and see what he thought.
"Maybe Erling asked him to swap, I don't know!"