...by asking every player what day it is. If they answer correctly that it's National Concussion Awareness Day... or September 15th... or Friday... or come fairly close to any of the responses above, they will be cleared to play this week.
You would think that they could devote a month to raise awareness...which would allow them to exploit by branding with a color in order to sell alternate merch and keeping 99% of the profits. They really dropped the ball here.