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Manchester city is in an unstable condition in this transfer window because they have to make a big effort in keeping their players from leaving in this transfer window. Previously, two of their core players had been recruited by other teams in this transfer window, such as Gundogan who was recruited by Barcelona and Mahrez who was bought by Al Ahli. So recently, news has emerged that Bernardo Silva has started to be linked with a number of big teams in Europe and that Kyle Walker has also been eyed by a big Bundesliga team.
I think Manchester city should be able to hold Bernardo Silva and Kyle Walker for next season because they had a big influence on Manchester City game last season. So Pep Guardiola has to watch out for that if he doesn't want to lose a lot of their star players in this season's transfer window.
I don't think Pep Guardiola will be as worried as you say. Manchester City have players who can still be relied on like Foden if Bernardo Silva leaves during the transfer market. Pep Guardiola also has good defenders where it is possible to replace Walker who other teams are interested in, but of course it is important to try to keep those two players as much as you can.
Even though Manchester City ended up having to part ways with their 4 important players during the transfer market, so I don't think they will lose a lot of quality which can make their title chances lower. Pep Guardiola definitely has a good plan in mind for his team, he will also anticipate other plans should Walker and Silva leave.