The Belgium playmaker only lasted 23 minutes of the season opener at Turf Moor.
Pep Guardiola says Manchester City star Kevin De Bruyne could be out for up to four months and may require surgery on a hamstring injury.
The 32-year-old was forced off in the first half of June’s UEFA Champions League final triumph against Inter Milan and did not play a single minute of pre-season.
De Bruyne returned from that hamstring problem as a second-half substitute in the Community Shield defeat to Arsenal and captained the side against Burnley in Friday’s Premier League opener.
But the Belgian playmaker lasted only 23 minutes at Turf Moor, where he seemingly out of nowhere signaled to the bench that he felt something.
Guardiola said after the Burnley game that the problem involved the same hamstring and that he would be out for a few weeks, but it appears to be worse than first feared.
“It’s serious, the injury,” said the City boss. “We have to decide if it will be surgery or not, but it will be a few months.
Guardiola said a decision would be made in the “next few days” and De Bruyne faces “three or four months” if he goes under the knife.
“Ramon (Cugat) saw the pictures,” Guardiola said of his Barcelona doctor.
“He didn’t do anything personally, and they have two or three doctors who are more or less of the same opinion about what to do.”
Guardiola was speaking on the eve of City’s first ever UEFA Super Cup appearance, with De Bruyne’s injury clearly defeating him in Greece.
“I have to say that Kevin’s injury is a painful blow for us, so it’s a big loss,” Guardiola told a press conference ahead of the clash with Sevilla.
“Kevin has specific qualities that you can lose for one game, two games, but for a long time it’s really, really difficult for us.
“But at the same time you have to look ahead and of course you have alternatives there with different skills because the skills for Kevin are irreplaceable.
“But you have different talented players so it’s an opportunity. Life gives it to you.
“When there’s an injury there’s an opportunity for others and I’m sure they’ll take it.”
Asked if the injury was down to bad luck or De Bruyne’s return too soon, Guardiola said: “Give me 25 days to prepare and he won’t get injured.
“Before I decided, I spoke to the doctors, the physiotherapist with him and he told me that I feel good, I feel good.
“So I said ‘ok, it’s better to start than half (take him off), but unfortunately that’s what happened.’
Phil Foden appears set to step into that role, but given the severity of De Bruyne’s injury, City could look to sign before the window closes.
“We’ll see,” he said. “After what happened, we didn’t speak to Txiki (Begiristain, City’s sporting director).
“We will see chances and possibilities. We’ll see.”
De Bruyne looks set to miss City’s entire Champions League group stage and possibly the Club World Cup in December, in addition to domestic affairs.
The severity of the Belgian playmaker’s injury is a major setback and came as a surprise to team-mate Rodri.
“Well, I honestly didn’t know there were that many,” he said. “What can I say? I think he is one of the most important players for the club.
“We will definitely miss him a lot. We will try to support him in this bad time. Nobody wants to get hurt.
“I saw him the other day and he was positive, he wants to come back (quickly).
“He’s an experienced player, he knows he doesn’t have to run fast to come back. He has to recover – that’s the most important thing.
“We will miss him, but at the same time I can tell you that we have a full squad to play the two months without him.
“And hopefully we can have him back because he was so important in those years.