I've mentioned times without number that the problem with Chelsea lies on their coach, I feel like he lacked the ability to effectively manage the players at his disposal. I don't think it is true to say that Chelsea lacks the squad depth they require to challenge the status quo but lacks the ability for effective management of those players. We have the likes of Romelu Lukaku who haven't been used effectively yet a lot of money have been spent on his transfer and so on.
Personally, I think the problem is both and indeed yeah the coach is probably the main factor, when the new coach is unable to make all the players into a solid team then the results are not optimal. Apart from that, Chelsea management also has the same role in Chelsea's failures in the last few seasons, they are impatient and want to see instant results while sometimes coaches need more time to change the team for the better.
The coach will be the first person to blame when a team fails to perform well, but we also have to see how Chelsea management always makes hasty decisions regarding their coach. The reason is that they don't give the coach much time, in fact they only give the coach one season and then they fire him.
Many teams fail in their first season with their coach, but in their second season many finally make good progress and now Chelsea is not doing that.
Pochettino, for example, had to be fired at the end of this season, even though in terms of his game I think he could show progress, Chelsea were not satisfied so they fired him. It is very difficult for a coach if he is only given a very short time.
A manager should be held responsible when the team performance is not good even after all the opportunities are given to the manager. No matter how much experience a manager appoints to a weak team, he cannot do well against strong teams with those weak players. I would like to blame some of the management for Chelsea's poor performance as we have been seeing their manager change for a few seasons now. Every season we see them appointing new managers and a manager at the club can only do one lentil at most but they don't give any manager a chance to improve. No manager can give his best for the team in just 1 season, so in this case, Chelsea must appoint a competent manager for more than one season, hoping that this appointment will improve the performance of their team.