Manchester City striker Sergio Aguero says “everything went well” after having surgery on his injured knee.
The Argentine had travelled to Barcelona to see a knee specialist amid fears his season might be over.
His manager Pep Guardiola said it is too early to put a timescale on the 32-year-old’s return to action.
Asked if Aguero would be fit for the resumption of the Champions League on 7-8 August, City’s Spanish boss said: “I don’t know right now.”
He added: “Once he has finished the surgery we will know the time Sergio will come back to play with us.”
Aguero was forced off before half-time in the home side’s 5-0 Premier League win over Burnley on Monday, following a challenge by defender Ben Mee.
However, in his post-match interviews, Guardiola revealed Aguero had a knee problem before the match.
City are due to face Real Madrid in the second leg of their Champions League last-16 tie with a 2-1 lead from the first leg in Spain.
On Wednesday the player tweeted: “Everything went well and I will soon start with the recovery.
“Thank you so much to Dr. Cugat and his team and everyone for so much support.”
Meanwhile Chelsea manager Frank Lampard says he will have no thoughts on the Premier League title race when his side entertain City on Thursday evening (20:15 BST).
If Liverpool beat Crystal Palace on Wednesday, City will need to win at Stamford Bridge to keep the title race alive for another week before they play Liverpool on 2 July.
“I am aware of the situation, but I can only focus on us,” said Lampard, whose side currently sit fourth in the table, four points behind third-placed Leicester, with a game in hand.
“I have had absolutely no thought of Liverpool’s situation, it makes no odds to us at all.
“We respect Liverpool and Manchester City as two fantastic teams, in the last two to three seasons they’ve been dominant, but we can only look at what this match means for us.
“We have a job to do and our job is to go up against one of the best teams in the world over the last few seasons and try to get a result.”