The Premier League champions announced on Wednesday afternoon that the Belgium midfielder was undergoing tests on his right knee after suffering a knock in training earlier that day.
While Man City are not yet sure of the full extent of De Bruyne's injury, a number of reports have claimed that the 27-year-old may be sidelined for at least two months.
"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," Walker told Sky Sports News.
"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."
De Bruyne made 52 appearances in all competitions for Man City last term, scoring 12 goals and registering 21 assists.