Manchester City's Argentina striker Sergio Aguero has undergone knee surgery and it was not clear when he will be fit again, admitted manager Pep Guardiola.
The club's record goalscorer limped off during Monday's 5-0 Premier League thrashing of Burnley at the Etihad Staidum.
Guardiola said after the game he feared the 32-year-old could miss the rest of the league season which ends in July.
The Argentine flew to Barcelona on Tuesday to have specialist Dr Ramon Cugat look at his knee and City will be hoping the player might return in time for the Champions League restart in August.
Asked on Wednesday if Aguero would be fit for the resumption of the European football's premier club competition on August 7-8, City's Spanish manager said: "I don't know right now. Once he has finished the surgery we will know the time Sergio will come back to play with us."
Guardiola had suggested that the Argentine would have the operation on his left knee on Thursday but Aguero later tweeted suggesting the procedure had already taken place.
Posting a message alongside a picture of himself in a hospital bed, Aguero wrote: "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."
City lead 2-1 against Real Madrid after the away leg of their last-16 match and are hoping to reach the 'Final Eight' of the competition which will be held in Lisbon.
Guardiola said City had plenty of options, with Gabriel Jesus the only main striker fit and ready but Ilkay Gundogan and Raheem Sterling are able to slot into the role.
The manager indicated defender John Stones was close to a return after an ankle injury but was unlikely to face Chelsea.
"He is on the pitch training and getting better," said the Spaniard. "Hopefully in the next few days he can play in the team."
A final decision on whether City's clash against Liverpool next Thursday takes place at the Etihad Stadium or a neutral venue is expected to be made before the end of the week.
Asked about the possibility of the game being moved elsewhere, Guardiola said: "We will follow the Premier League instructions. All the protocols they've said, we're going to do."




























