Visibly in pain, concerned players surrounded Webb, but it was Vardy who grabbed the ref's whistle and blew it to bring a stop to the match. Since the ethos of soccer is to play until the whistle and Webb was unable to,

David Webb was inadvertently struck in the side of the head by Leicester forward Jordan Ayew as he ran past him.

Jamie Vardy blows referee’s whistle to stop Leicester-Southampton game after official suffers head injury - Referee David Webb went down with a knock to his head after an accidental collision with Lec