The geometry of the soccer goalkeeper, or goalie, position can be summarized by the expression "playing the angles." Other than possessing the ability to catch a ball struck toward the net, as well as being sufficiently agile to dive to block or cover shots, a goalie's understanding of the angles at which balls will be directed at the goal will usually decide goal-tending success or failure. The goalkeeper, the last line of defense on the soccer field, is responsible for the protection of a goal that is 24 ft wide and 8 ft high (7.3 m and 2.3 m). As a basic geometric proposition, the closer the goalie can get to the shooter, the less net area the shooter has available as a target.
The understanding of goalie geometry is not restricted to the horizontal angles of a shot toward the goal. The goalie must also appreciate the vertical geometry of the flight of the ball, an understanding of the fact that the ball can be directed along a horizontal and a vertical axis. When the goalie may cut down a shooter's angle by moving closer to the shooter, the goalie may then become vulnerable to a shot lofted above the goalie, known as a "chip."
There are three specialized situations in which goaltender angle play is of particular importance: the corner kick, the free kick, and the breakaway.
A corner kick arises on a number of occasions in the course of a soccer game, where the ball is kicked or directed past the goal line by a defender. The corner kick is an offensive set piece, with the offensive players moving in a coordinated attack as soon as the ball is struck. The goalie must be positioned at the place in the goal crease where he/she can move most efficiently to block either a kick, a volley, or a header that will be attempted on the corner kick.
A free kick is awarded on a defensive foul that occurs outside of the penalty area. A defending team will usually set up a wall of five or six defenders; the offensive player will either attempt to bend the ball with a spinning kick around the wall for a direct shot on goal, or fake the direct kick and pass to a teammate who has a better shooting angle on the goal, avoiding the wall. The goalie's optimum position will depend on the angle between the ball placement and the goal; commonly, the goalie takes up a position where he/she can see around the wall, without entirely eliminating his/her ability to move laterally along the goal line to respond to the kick.
A breakaway is the greatest challenge faced by a soccer goalie. If the goalkeeper is positioned at the goal line waiting for the shooter to make a move, the shooter will control the angle and be able to move to his/her most desired position to take a shot. If the goalie rushes at the shooter to cut down the angle,