It halts play and guarantees that a badly wounded player is evacuated from the field of play. Only when a goalie is injured is there an exception to the necessity to leave the field of play. A goalie and an outfielder have collided and require medical treatment. Instead of leaving the field, the pitcher remains in the game. There is no rule that requires you to leave the playing field after receiving medical attention. However, most sports organizations have their own guidelines regarding player injury rehabilitation, which may include restrictions on how long a player can remain in the game. The NFL, for example, allows players to return to the field after receiving medical treatment but if they are re-injured they must sit out again. In general, people who have received medical attention but are not prevented from further participation during the game or practice session by the rules of their sport should leave the field once healed. This is particularly important for players who have been treated for an injury that could be aggravated by continued exercise. For example, someone who has had an ankle sprain should not be forced to continue running after the injury has been treated. Some injuries need to be protected against during play. This includes any form of concussion. Thus, after receiving treatment a player should be removed from the field of play unless it is clear that he is able to resume participation without further harm to himself or to others.