The Premier League champions have revealed that the Belgium international will miss up to three months of action after suffering the issue in training earlier this week.
De Bruyne played an instrumental role for City last season before representing his country at the World Cup, and Guardiola feels that fatigue has led to the playmaker breaking down at the start of the new campaign.
At a press conference, Guardiola told reporters: "He will be out for two-and-a-half months to three months. Hopefully in that time he can do as well as possible to be back and help us again.
"He will be a big miss like Benjamin Mendy was last season. Kevin was outstanding last season and of course for him and his family, these injuries are never wanted.
"They are accepted, they are part of the game. Sometimes these things happen. [The players] don't rest, they have a tough, tough season last season. Human beings have a limit. I'm pretty sure this can be an influence. When you are fresh in your legs, this doesn't happen."
De Bruyne only made an appearance from the bench as City beat Arsenal at the Emirates Stadium last weekend.