The goalkeeper is the most specialised position in football. A goalkeeper’s job is mainly defensive: to guard the team’s goal from being breached (to not let the other team score). Goalkeeper is the only position defined in the Laws of the Game. Goalkeepers are the only players allowed to touch the ball with their hands and arms, however they are restricted to doing so only within their penalty area; for this reason, they must wear jerseys that distinguish them from other outfield players and the referee.
If a goalkeeper is sent off or injured, and there is no substitute goalkeeper available, an outfield player must take the goalkeeper’s place and put on the appropriate identifying uniform.  The discipline of goalkeeping is so specialised that it is very rare in the professional game for a goalkeeper to play in any other position. One notable exception is Jorge Campos of Mexico, who played effectively as a striker when called upon. 4] A goalkeeper with good technical skill may opt to take his team’s penalties and free kicks though this is rare as the goalkeeper would be caught out of position if possession is conceded immediately after the kick. Jose Luis Chilavert, formerly of Velez Sarsfield and Paraguay, and Rogerio Ceni of Sao Paulo and Brazil are well-known free-kick and penalty specialists with over 100 goals to their names. Hans-Jorg Butt is the goalkeeper to have scored in the most different competitions, having scored in all of Germany’s top four divisions, the German cup and the UEFA Champions League. 5] Physical strength, height, jumping ability and judgement are valued qualities for goalkeepers to have in order to deal with aerial balls and agility, quick reactions and a good positional sense are all needed for shot stopping.  The standard football skills of ball control, tackling, passing and dribbling are not usually required in a goalkeeper, although the introduction of the back-pass rule in the early 1990s has necessitated improvement on such skills.