Kelvin De Bruyne's injury is one that'll last a while and may likely cause him to loose from upon recovery, he'd need some time off to get back himself and his agility to match Guardiola's football, he's a quick picking player and he's going to be able to bounce back, no doubt City misses him as he's got this special effect he gives to the team, a few things has changed since his absence and his absence is felt in a minut level.
Man City's strength decreased quite a lot when De Bruyne was hit by an injury which forced him to be absent for several months and even now he has not been able to strengthen the team again. The recovery must be truly total and maximal so that undesirable things don't happen again. Man City is currently even worse. There are several other big players who were injured while they were strengthening their country's national team. Even Haalan and I are currently suffering from injuries. This is really bad, because after all, Man City's strength will decline again.
What's more, they will play against several strong teams in the EPL and also in the UCL, so they will definitely have their own challenges if they have to play without these players. Soon they will face Liverpool and also Tottenham, which incidentally cannot be underestimated.