Manchester City manager Manuel Pellegrini has ruled top scorer Sergio Aguero out of Wednesday's crucial Champions League game against Roma, and admitted that it was impossible to know how long the injured Argentinian would be sidelined.
The star striker hobbled off in Saturday's 1-0 win over Everton with damaged knee ligaments.
The Argentina international, the Premier League's top scorer with 14 goals, was hurt in the second minute when he jarred his knee as he stretched for the ball in a challenge with Muhamed Besic.
City's medical staff were set to assess Aguero yesterday to determine the extent of the injury and how long they expect the 26-year-old to be on the sidelines.
Pellegrini has already ruled Aguero out of the game against Roma, in which City must better CSKA Moscow's result against Bayern Munich to progress to the knockout stage.
Pellegrini said: "He will not play against Roma and that is a very important game. It's impossible to know how long he will be out.
"It's very difficult if you have trouble in your ligament to recover in a few days. Of course it's a big problem, because Sergio was in a very good moment and is an important player for our team."
Premier League leaders Chelsea slipped to a 2-1 loss to Newcastle earlier in the day, which meant that City's victory moved them to within three points of the London club.
The victory over Everton came thanks to Yaya Toure's 24th-minute penalty, and Pellegrini said that it proved his side are not just a one-man team reliant on Aguero.
"This team is not just Sergio Aguero," Pellegrini added.
"The way we won was important for what we showed in defence.
"The defence...are criticised a lot, but I thought they did very well.
"Chelsea lost their game and it was important to recover the points and to be near the leaders.
"December is a very different month when we have to play a lot of games. It's a month in which you don't win the title as such, but it is a key month to try to start the next year near the top."