Coach has an important role in a team and players are a supporting factor in achieving success. If the coach does not have tactics and strategies in placing players then the results will not be good because they will not be able to play at their best level.
Certainly, apart from the players, the coach is one of the factors in how the club will actually perform and develop. Coaches play a very essential role in managing, developing, guiding, directing, optimizing players, and creating strategies and tactics that best suit the conditions of their team. Not only that, the coach must also be smart in determining tactics that are appropriate and good for the match at that time and also during the course of the match. Because it could be that one match requires different tactics.
However, on the other hand, sometimes, a coach who is very good at one club may not necessarily be that good when he moves to another club. Currently, we already know several good coaches and pros who are successful at clubs, but are not very successful or appear to be failures at other clubs. Because sometimes it doesn't suit the style of play, the condition of the players, and also the condition of the club itself. Like Rudi Garcia currently at Napoli, even though he is a professional and good coach, but up to now, he still hasn't been able to optimize his abilities to make Napoli much better than before. Because there are other factors that influence it, or because he really needs more time to adapt.