For a preview of what evidence on Day 1 of an NHL concussions trial might look like, head over to YouTube, type in "NHL brawls" and take your pick of any of the 481,000 choices offered there. In a league where both sides give a wink to bare-fisted fighting — and in a case in which raw emotion could play as big a role as the still-developing science of concussions — it will be hard for either the players or the NHL to claim the moral high ground. A group of 10 retired players, seizing the moment in wake of the $765 million settlement the NFL recently offered its concussed retirees, filed a class-action lawsuit on Monday.