The most important person at any football club is the head coach more known as the football manager.
The manager has the final say in who plays in each match, what are the tactics to be used for each game, and any substitutions and tactical changes during a football match. He is also responsible for the buying and selling of players, giving the boss much greater control over the roster.
Every football manager has different approaches and styles in running a football club. Some are highly tactical, insisting their players work within a rigidly defined predetermined system. Other managers implement by the force showing their personality, either charismatically or through fear and discipline.
Manager Brian Clough, for example, led Nottingham Forest to the 1979 and 1980 European Cups, yet paid no heed to tactical systems whatsoever. Managing on gut instinct, he either shouted and bawled at his players, or put a comforting arm around them, depending on his mood. Occasionally, he would even get them drunk before a game. Idiosyncratic, maybe, but it worked.
The playing style of a team and sometimes the entire club rests on the personality of the one in-charge, the Manager. This goes some way to explaining why, if the team embarks on a losing streak, the Manager is usually the first person to be replaced.