The two boys with the baseball bats represent the pain he feels from her. He doesn't see them because he doesn't want to admit that this girl does not feel for him the feelings that he feels for her. Throughout the video, he is going through events that would normally either kill or cause severe 'pain' to someone, such as staying underwater, falling down the stairs, jumping into the window, etc. Yet you will notice that he always just gets up as if he is totally unaffected.