Kevin de Bruyne could miss the next four months of the season as Manchester City decide whether he needs surgery on a hamstring injury, manager Pep Guardiola says.
The 32-year-old limped off after 23 minutes in City's opening win against Burnley at Turf Moor on Friday.
De Bruyne also went off injured during the Champions League final win over Inter Milan in June.
"It's a serious injury," said Guardiola.
The Belgium international missed all of City's pre-season matches and returned as a second-half substitute in the Community Shield defeat by Arsenal.
"We have to decide if he needs surgery or no surgery but he will be out for a few months," added Guardiola, who confirmed De Bruyne's issue is related to the same hamstring.
"The decision on surgery will be taken in the coming days and could see him miss three or four months".
De Bruyne scored 10 goals and provided 31 assists as City claimed the Champions League, Premier League and FA Cup last season.
He said earlier this month he had been playing through the pain with a hamstring injury for the final two months of the season, but Guardiola said every precaution had been taken before the game against Burnley.
"We could say don't play but this injury could happen later," the Spanish boss said. "Before I took the decision I spoke to the doctor, the physio and him. He said he felt good.
"I have to say the injury for Kevin is a blow for us. It's a big loss. Kevin has specific qualities which you can lose for one or two games but, for a long time, it is really tough for us.
"At the same time you have to look forward, you have alternatives there - of course different skills, as the skills from Kevin are irreplaceable.
"We have a different talent of players and this is an opportunity; life gives you that. When there is an injury there is an opportunity for the other one, so I'm pretty sure they will take it."
As to whether City will try and bring in reinforcements before the transfer window closes, Guardiola said: "We will see. After what happened we will see the possibilities."
City face Europa League winners Sevilla in the Super Cup in Athens, Greece on Wednesday at 20:00 BST.
Source: BBC