After sustaining the injury in training on Wednesday, De Bruyne appeared at the premiere of All or Nothing, a documentary about last season's champions to be aired on Amazon Prime, on crutches and with his right knee in a brace.
'No surgery is required, and the midfielder is expected to be out for around three months. "Everyone at City wishes him a speedy return to action".
That means the Belgium worldwide will miss City's first four Champions League group fixtures as well as potentially crucial domestic games at Liverpool and Tottenham on October 7 and 28 respectively.
De Bruyne had just returned to training August 6 after helping Belgium to the semifinals of the World Cup in Russian Federation.
De Bruyne, who enjoyed a superb World Cup as Belgium reached the semi-finals, suffered a similar injury in a league game with Everton in January 2016 although that kept him out of the team for two months.
Guardiola will be keen not to rush the midfielder back, however, and as you will no doubt be aware, has enough playmaking ability in the City squad in the shape of the increasingly impressive Bernardo Silva, David Silva, Riyad Mahrez and Ilkay Gundogan to cope with De Bruyne's absence.