De Bruyne is understood to have torn the ligaments in his right knee in what is described as a freak accident.
City will certainly miss the 27-year-old, but have a wealth of options for the position he usually occupies.
According to www.metro.co.uk, De Bruyne faces around two months out after suffering the injury when he caught his studs in the turf before leaving the training ground on crutches.
"So I hope this one will be similar, especially in terms of the way we play and in terms of winning".
City do, however, have David Silva, Bernardo Silva and Gundogan who can offset his loss in midfield.
"He is very important".
Gundogan and Fernandinho were speaking at the world premiere of All or Nothing: Manchester City, available on Amazon Prime Video from Thursday.