Chelsea have the history of winning the Champions League in the condition of the team not going well in the English League, but this season cannot be used as a reference that Chelsea can repeat the same thing. The midfield is indeed quite crucial because it is the brain of a series of attacks that are trying to be built and if the attack line is creative enough in building attacks it will be easier for strikers to score goals. Of course all crucial positions in football and I don't think Chelsea have not lacked good players, it's just that so far it has not been fully maximized in contributing to the team.
Chelsea winning the champions league in the past is difference from now and their performance should be used to determine how far they stand a chance to go far in the competition, they have a good squad but their first outing in the league doesn't show that the squad is strong enough to face big teams in the champions League. Their attack is weak, their midfield wasn't very active against Crystal Palace if they have good players they should start showing that in the teams performance not just the name of the players alone.
Chelsea is a good team but the manager should focus on targeting a win in every match they play he shouldn't just complain to the team they should work it out in training and get the best result in every game if they must achieve a good record this season.