Kevin De Bruyne could be out of action for up to four months after suffering a hamstring injury in the opening Premier League game of the season, manager Pep Guardiola said on the eve of their UEFA Super Cup clash against Sevilla.
The Belgium international left the field in the 36th minute of City's 3-0 win at Burnley on Friday.
De Bruyne, who was left out of City's squad for their Super Cup game, also limped off during the Champions League final in June and Guardiola confirmed the midfielder had suffered a recurrence of the same injury.
"It's serious. We have to decide surgery or no surgery but he will be out for a few months," Guardiola told reporters on Tuesday.
"(A decision on surgery will be taken) in the next few days. It will be three or four months."
Asked if De Bruyne's injury occurred because he was rushed back into action before he was ready, Guardiola said: "We could say 'don't play' but this injury could happen later.
"Before I took the decision I spoke to the doctor, the physio and him. He said he felt good.
"We will see (about signing a replacement for De Bruyne). After what happened we will see the possibilities."
Guardiola wary of dangerous Sevilla
City will play Europa League winners Sevilla in Athens in their first-ever appearance in the UEFA Super Cup.
The Premier League champions qualified for the Super Cup after clinching their maiden Champions League title in June following years of heartbreak on Europe's biggest stage.
Asked how he felt about finally winning the Champions League with the Manchester club, Guardiola said: "It is a relief for the club. It's always difficult to win.
"Of course it is a relief but it is not enough otherwise we would be at home. We are hungry enough to compete and challenge ourselves. If someone wants to take out three crowns they will have to fight to take it."
City can add another European title to their trophy cabinet on Wednesday with a win over Sevilla - who have won the Europa League a record seven times.
Sevilla have lost five out of the six Super Cups they have contested, but Guardiola stressed that it was "not easy" to qualify for European football's curtain-raiser, adding that City will be wary of the threat posed by the Spanish team.
"Sevilla have special character, it's something in the DNA that makes this team different. They will be dangerous against us," Guardiola said.
"You cannot imagine how happy that we are to play the Super Cup because we won the Champions League. Who knows when we will come back here to win this tournament?"
Reuters