"Kirk Muller doesn't know if he suffered a concussion during his playing career. Sure, he got hit in the head, but they weren't diagnosed in the same way.

Now the Carolina Hurricanes' coach, Muller's playing days ended before the 2004-05 lockout. Washington Capitals right wing Mike Knuble's career has spanned the time when it was called "getting your bell rung" and nothing more to an era of quiet rooms and protocol where it's recognized as a brain injury.

"Back in the olden days you just shook it off, seeing stars and all that," Knuble said."