It is a tough call, no question. Some athletes have successfully returned to hockey after prolonged concussions. Others have sustained further concussions and have had significant problems later on. And as Mark points out, some of the effects may not be felt until years or decades later.

My doctor said that what we do know is subsequent concussions generally have longer-lasting and/or more severe symptoms. So if Crosby ends up being out for 10, 12, 14, 16 months or more, what effect is the next hit going to have on him?

I also wonder about Crosby's ability to withstand heavy/jarring body-checking, not just hits to the head. NHL hockey is a fast, physical game.

In any event, he's still young and has lots of time to work out what's best for his health and hockey career.