Manchester City forward Sergio Aguero said there was a "strange" feeling in his knee when he sustained a potentially serious injury against Everton on Saturday, manager Manuel Pellegrini has revealed.
City have already ruled their 19-goal top scorer out of Wednesday's Champions League decider against Roma.
The Premier League champions are waiting to discover the full extent of the Argentine's problems amid suggestions that he could be out for around a month.
Aguero was in tears as he came off after being hurt in the second minute of City's 1-0 win, and Pellegrini told national newspapers: "He had pain in his knee, and he told us he felt something strange happen."
The forward scored a hat-trick in City's last Champions League game, a 3-2 win over Bayern Munich, and has delivered five goals in his last three European matches.
But while Pellegrini described Aguero as being in the same bracket as the two best players in the world, he insisted City could prevail without him.
"Every big team must have important players like Sergio," he added. "I suppose [Cristiano] Ronaldo is very important for Real Madrid and [Lionel] Messi is very important for Barcelona, but neither of those teams are all about just one player.
"We would prefer to play with Sergio but, if he cannot play, we must try to continue the same way we have been playing in the last week.
"Remember, last season we played a lot of games without Sergio -- and these are the same players and the same team."
City are already without the suspended Yaya Toure against Roma and are waiting to see whether David Silva and Vincent Kompany will be fit to face the Serie A runners-up.
In attack, Edin Dzeko, who had been out for a month, made his comeback as a second-half substitute on Saturday, while Stevan Jovetic missed that match with a minor knock but is expected to be fit to face Roma.
Pellegrini added: "We have beaten a very difficult team like Everton without Sergio, without Silva, without Kompany, without Jovetic and with Dzeko only able to play 20 minutes."