Of course it should! There is nothing in the rules that states that if an opposition player is injured you have to kick the ball out of play. Villa should have played to the whistle and asked questions afterwards. I'm fed up with players losing possession, going down injured and expecting the opposition to kick the ball out of play. It is up to the referee to stop the game if he thinks it necessary. I agree that Villa did kick the ball out when a Leeds player was injured and morally Leeds should probably have done the same. However, in my opinion it should be left up to the referee and the game should continue unless he thinks the game should be stopped. In this way it would stop players going down and feigning injury.