Sergio Aguero is facing a race against time to be fit for the resumption of the Champions League after the Manchester City striker had surgery to correct his left knee injury.
Aguero limped off during the 5-0 victory over Burnley and after travelling to Barcelona on Tuesday to be examined by Dr. Ramon Cugat, the 32-year-old required an operation.
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The Argentina star posted on Twitter on Wednesday that "everything went well, and I'll soon begin recovery. A big thanks to Dr Cugat and his team -- and to all of you for your support."
Manchester City Pep Guardiola told a Zoom news conference earlier on Wednesday that he wasn't sure when Aguero would return to the pitch.
"Once he finishes maybe we'll know exactly the time when he can come back and join us and play with us," Guardiola said.
Aguero is expected to miss City's last eight Premier League games, including the trip to Chelsea on Thursday, but there is still hope he could return in time to feature against Real Madrid in August in the delayed round-of-16 second leg tie.
UEFA have scheduled the remaining round-of-16 fixtures for Aug. 7 and 8.
Guardiola listed Gabriel Jesus, Raheem Sterling, Bernardo Silva and midfielder Ilkay Gundogan as the players he could use to fill the void left by Aguero.
City face Chelsea at Stamford Bridge on Thursday night but Guardiola said, with little left to play for in the league, he will prioritise Sunday's FA Cup quarterfinal with Newcastle United at St James' Park.
"We can't deny that we have one eye on Newcastle," he said. "Chelsea and Liverpool are prestigious but Newcastle is one game. A final. We have one eye.
"It depends on the physical condition, the minutes they have played. We take a look a little bit at what is going to happen, not just Chelsea."