Manchester - Manchester City manager Pep Guardiola admitted on Friday he does not know when Vincent Kompany will return, sparking fresh worries about the veteran defender's long-term fitness.
City skipper Kompany has been absent since he injured his calf in August while on international duty with Belgium and has not featured for his club since a 2-1 win at Bournemouth on August 26.
It was initially hoped the 31-year-old centre-back would only face a short spell on the sidelines but his ongoing absence has raised fresh concerns.
Kompany has endured a difficult few years with injury and has made just 28 appearances in the Premier League in the past three seasons.
When asked for an update on his fitness, Guardiola said the centre-back was not ready and he did not know when he would be return.
Guardiola, speaking at his weekly press conference in Manchester, is likely to restore Sergio Aguero to his starting line-up against Burnley on Saturday after he said the striker was ready to feature against the Clarets.
It had been thought the Argentina international could be missing for six weeks after he suffered a broken rib in a car accident in Amsterdam late last month.
But Aguero has been an unused substitute in City's past two matches - a 7-2 win over Stoke in the Premier League and a 2-1 success against Napoli in the Champions League.
"He was ready to start (against Napoli)," explained Guardiola, who has no fresh injury worries ahead of the match at the Etihad Stadium.
"I think the game against Stoke it was just one training session before. He could have played but was not completely fit.
"But the game against Napoli he was ready and of course he is ready for tomorrow against Burnley."
Despite City's scintillating form that has propelled them to the top of the Premier League, Guardiola has warned his players not to underestimate Burnley after improved results from Sean Dyche's side away from home this season.
The Clarets have beaten champions Chelsea and Everton away from home and secured hard-fought draws at Liverpool and Tottenham.
"I have a lot of respect for what they have done," Guardiola said. "Last season they had problems to win away but in the first game at Stamford Bridge they took points and also then at Anfield, against Tottenham, then win with an amazing result at Goodison Park.
"What they do, they do really well. They are masters in the channels, with long balls, the second balls, in set-pieces and defend well in the box.
"It's complicated to attack them because they are physically strong. We have to try to be dynamic, try to take advantage because when they score goals they defend really well and their results away are fantastic."
And Guardiola believes there is still more to come from his players even though they have produced some eye-catching displays in recent weeks.
"Everybody can improve, myself, everyone," added Guardiola. "I said many times in the last few weeks we have played quite good in the last games but always we can improve. Always we can do better and hopefully we can maintain that level in the next games."