Considering the experience and tactical ability of Pep Guardiola and the current squad of Manchester City, I think the club wouldn't feel any significant effect about the players that's left the club this summer transfer window.
IIkay Gundogan after his departure was immidiately replaced by Mateo Kovacic while Riyad Mahrez who's yet to be replaced wasn't a regular starter last season. The transfer window is still open which means that City can still sign few more players before the end of the transfer window. But even if they fail to make any more signing, City will still perform well in Europe
Manchester City is set to confront fresh challenges after winning the UEFA Champions League title; they are the current reigning Champions and widely regarded as the best club in the world. Pep Guardiola does not appear concerned about his departing players; perhaps he has a backup substitute for every key player at the club. Chelsea's Kovacic will take over for Ilkay Gundogan. Manchester City's performance would be smoother than ever before, thanks to Pep's relentless work on the club's anticipated performance, always ready to take things to the next level.
although there is no guarantee about this, it makes me a little more sure because this season Man City has not made many changes to their line-up despite losing several players, but they still have reliable players like Haaland and my belief is based because all Man City players have good consistency. very high and very solid in every game so dont rely on certain players even every player has the opportunity to score like last season maybe Haaland was able to perform well in the EPL but in the champions league not too good but instead other players performed very well so Im very sure if Pep still have the goal to get the champions league trophy again and that for sure.