Manchester City won the Champions League title in the last season and obviously, that's a good reason to say they are the favorite team for the tournament even during this the season but the fact about Manchester City and Pep Guardiola is they lost some power. Manchester City sold some players and they couldn't spend money and buy better players like other teams did during the summer and that's why I think other teams like Bayern Munich will have more chance of this.
Yes, Man City is one of the favorite teams to win UCL trophy because they are the winner in the last year. But they are no longer the Man City as in the last season. Man City becomes weaker if we compare their strength in the previous season. That's why Man City experienced some losses lately, they have a weak area in their lineup. It is true that some players of Man City moved to other teams. They ruined the expectation of Man City management.
Manchester City are favourites,but they can't win the Champions league this season,to me,they lost a little depth in their squad when Mahrez and Gundogan left the team.It is true that Gundogan was a very good player at City,and his presence in the team then was really helpful to City.He was responsible for scoring important goals,just the way Rodri is now in the current squad,thats how Gundogan was.However,they go again in the race to win the Champions league two times,but I don't see that as a possiblity because so many good teams are also eyeing that trophy.Barcelona,Bayern,Dortmund,and PSG and Arsenal are all hoping lift that trophy, therefore,it's really going to be a tough one.