Meh, yes and no. When I had my last concussion, I had headaches for weeks, then a few days symptom free and the minute I got my heart rate elevated I got nauseous from the vertigo and aches. It means nothing. Every concussion is different.
and as a GWOW said, I have no idea how sports lasted this long with athletes underestimating concussions. Just yesterday, I was watchin Sound FX on the NFL Network, when they had Mike Shanahan mic'ed up, and in one of those, his RB was like, "Coach, I can't see (from the concussion)" Shannahan responded, you don't need to see, we're going to go play action. It just makes you think..wow. Or stories of Richard Sherman a few years back, he said he played the entire 2nd half of the game blind in 1 eye from a hit he took to the head.
I thought Terrel Davis had migraines that were unrelated to a concussion. I may well be wrong.