I do not think there should be a lawsuit but.....yes the players know the risk going in. Just like a high steel worker putting up buildings. The employer still has to have policies in place that present a safe work space (of course within reason considering the sport). The culture of players playing injured runs very deep. As a hockey coach with A level kids I saw kids playing injured. We also made sure that if a kidd took a hit to the head that he did not play until we, the parents, and a doc said he was OK.
Pros should be the same. There is a world of difference having a culture where you play with a broken arm and one where you feel you have to play after recieving a concussion.
Yes, it is part of the sport and I am at the top of the list that calls Sidney Crosby a whiner and cry baby (hockey player). But if indeed his concussion was that severe then he did set the right example for NHL players, which are role model for kids, to speak up and say I need more time off.
Again, it is personal responisbility, but that falls on the coach, medical staff, and owners of professional clubs and trickles down to youth sports.