I am convinced that a coach can't responsible for everything. If thre are all these multi-millionaires and suddenly they don't know how to play anymore and lose one game after another, it is of course bad if the coach is no authority and can't get into the heads of the players, but blaming him alone or saying that didn't perform well is not the full answer to the question why Chelsea played like trash. The players should carry much more responsibility in those situations.
When a team starts losing one game after the other, the first person I look at is the coach. If this is a big team that has spent money on players and we know that these players are not very bad then we have to blame the coach. It is the job of the coach to make sure players play well. It is their job to make sure these players play the way he wants.
I'm not putting all the blame on the coach, didn't get me wrong, but the responsibility of that team lies in the coach. In the case of Chelsea, I'm very certain a bad coach was their problem. Chelsea couldn't win teams in the relegation zone and below mid-table teams, that tells you a lit. They also couldn't create enough chances (I know they didn't have the right midfield ) and they couldn't score goals.
Despite not having good goal scores and creators on their team last season, they should have done way better if they had a better coach.