Manchester City have confirmed that Kevin De Bruyne has been sent for tests on his right knee after suffering an injury in training.
Reports had been circulating of a serious problem for the Belgian international after he injured his right knee in training on Wednesday.
Although Premier League champions City later confirmed the injury, they insist that tests are still ongoing and that no prognosis has been made as yet.
"Kevin De Bruyne is undergoing tests on his right knee after sustaining an injury at training on Wednesday," said a statement on the club's website.
"The extent of the problem is not yet known and we will bring you further updates on Kevin's condition in due course."
De Bruyne could miss Liverpool game
The 27-year-old was City's Player of the Year last season after scoring 12 goals and setting up 21, and the injury must be a worry considering he previously missed 12 games in 2016 due to an injury to that same right knee.
Pep Guardiola's side do have a decent run of fixtures coming up should De Bruyne miss some playing time - as they face Huddersfield at home on Sunday before taking on Wolves and Newcastle before the international break.
If De Bruyne's injury is puts him out for longer than a month then City's home game with Fulham on September 15 and the start of their Champions League campaign the following week then comes into question.
Anything stretching into October would be a worry for City as they face away trips to Liverpool (October 7) and Tottenham (October 28) in the month.
City players react to De Bruyne blow
City midfielder Ilkay Gundogan, speaking at the premiere of the 'All or Nothing' documentary, said of De Bruyne: "He played an incredible season.
"He had so much impact on our game. He was maybe the main man for us last season.
"He is very important. We all hope that it is not too serious so he can get back on the training field as soon as possible."
City and England right-back Kyle Walker said: "Kevin is a great player and it's just unfortunate that it's happened to him in training but there's more than enough depth in the squad.
"We don't just rely on one player. It's a team game and whoever steps in will do well. Obviously it's a big loss but we've got more than enough cover."