De Bruyne suffered a ligament injury to the same knee in 2016 during a League Cup game against Everton which kept him sidelined for two months.
"The extent of the problem is not yet known and we will bring you further updates on Kevin's condition in due course".
However, with the season in its infancy and the transfer window closed, the Champions have now confirmed that their star midfielder is undergoing tests after sustaining an injury to his right knee in training this afternoon.
A similar recovery time this time round would see the Belgium global ruled out until at least November, but with the severity of the injury unknown, City manager Pep Guardiola will be left sweating over the results of his medical examinations.
His loss will be a major blow to Pep Guardiola after helping City to a record-breaking 100 points last season on the way to the title.
Bayer shares drop after Monsanto loses Roundup cancer trial
He noted that the US Environmental Protection Agency continued to assert - after repeated assessments - that Roundup was safe. The ruling came Friday afternoon after the Superior Court jury deliberated for more than two days, USA Today reported .
Celtic's Champions League hopes ended by AEK Athens
Asked if he felt frustrated on a night where defensive inadequacies proved costly, the Northern Irishman said: "Yes, of course". Croatian forward Marko Livaja's strike early in the second half left Celtic needing two unanswered goals to progress.