First of all, props for constructing this Tweetmail question as a haiku. I'll respond in kind (and then expound on that, because this is going to take more than 17 syllables).
Concussions are tough
Every one is different
The head is vital
Haydn Fleury, Jordan Staal and Micheal Ferland have each been diagnosed with concussions this season. In Fleury's case, it was clear when he sustained a concussion after taking a hard hit along the near wall in the neutral zone. In the cases of Ferland and Staal, the picture isn't as clear because there isn't one play you can pinpoint as being the root of the concussion, but both players reported feeling symptoms and were diagnosed.
Ferland was cleared through the concussion protocol and returned to game action on Tuesday, only to log just over five minutes of ice time in the first period.
"He's cleared all the hurdles as far as the protocol. He didn't feel great when he got out there, so we used caution," Brind'Amour said. "When he feels like he's ready to go, then we'll get him back in there."
What makes concussions so difficult and nuanced to assess is their unpredictability. After staying back east while the Canes made their way through California last week, Ferland rejoined the team at practice on Monday and felt fine. He participated in the morning skate on Tuesday and felt fine. He had been cleared through the concussion protocol. But, he didn't feel right in Tuesday's game.
"It's the right move. Always safety first," Brind'Amour said. "You always err on caution."