If you read any concussion protocol on return to play, it is very clear Sidney Crosby should not have been in the game in the first place. In most cases, it is a minimum of 7-10 days plus practice time with no symptoms before getting into game action.  For someone who has already had two serious concussions, there is no way he could have had a third concussion and returned to play 

http://fowlerkennedy.com/wp-content/uploads/2015/11/SPORT-CONCUSSION-RETURN-TO-PLAY-November-2015.pdf