Chelsea has got a whole lot of work to do on their team if they must make the best of this season. Number of players on a team doesn't matter and isn't a determinant wether the team is going to win or not and Chelsea is very much aware of this which they are supposed to take measures against it so it doesn't eventually get to cost them so much already before the end of the season. Manchester city has got three points ahead already on the table and it's really a smooth start for them and even helps their confidence. If Chelsea is able to get their squad right, most definitely they will become a better team just like they have been much before now
There is a lot to watch for at Chelsea as they navigate a new season and a new manager it may take time to see how they can adapt to each other, Chelsea may have lost the first game but we know their opponent is Manchester City and Chelsea still have many games left. I still believe that Chelsea still have the ability to compete in the top 4 at least we will wait until mid season, are you sure Chelsea will get a ticket to the Champions League next season?
There are several reasons why Chelsea lost and the first 2 reasons you have explained and the other reason is just because Chelsea also has to divide the match schedule in other competitions such as the European conference league play off round.
With all this we can see that the first defeat is not something bad because a club has its own goals and if Chelsea in the next match can be more consistent I am sure Chelsea can end the season with a ticket to the champions league.
All of this depends on how the Chelsea coach can manage the players well.
Nobody expected Chelsea to win against a team like Manchester City. City is a very strong team and Manchester City team was considered as favorite in this match. And naturally Manchester City won the match. However, it cannot be said that Chelsea's overall performance in this match was very poor. Chelsea have done enough to perform well.
Chelsea's goal is not the Premier League title. Chelsea's aim this season is to finish in the top four of the table and qualify for the Champions League. The team will also try for the Conference League title. Chelsea management should try to add Osimhen to the squad. With a talented scorer like Osimhen in Chelsea's squad, Chelsea's performance will be more stable.