You're right about the fact that both the player's and the couch plays a vital role towards ensuring the success of a team. And what most people do not understand is the fact that these two needs to work together, the player's needs to really submit to the leadership of the coach in order to for them to deliver effectively the coach's plans and strategies. It doesn't matter how good a player is, if he's not always following the scripts written by the coach, there'll always be a problem, it's just like a game of chess, while the Queen is the most flexible piece, it'll still depend on the expertise of the player before the Queen's potentials can be really onfolded. and same thing goes with the coach, it doesn't matter how strategic the coach is, if he can't get the player's to dance to his tune, the team will definitely fail.
So in a case where a team is failing, sometimes it could be a case where the players are no completely listening to the coach or a case where the coach isn't strategic enough. So sometimes it could be the fault of the player's and sometimes it's the coach, depending on the reason for the failure.