Calvin Johnson passed a concussion test two weeks ago to continue playing in the Detroit Lions' loss against the Vikings.

Johnson was on the receiving end of a helmet-to-helmet collision by Chad Greenway.

Greenway was fined $21,000 by the NFL for his hit.

Johnson admits that he actually did suffer a concussion.

"Yeah, you could tell. It was obvious," Johnson said. "I said exactly what I meant, but I guess you could take it out of context. What I meant when I said you have to keep going is you can't be afraid to go over the middle. Not that you get concussed you have to keep playing.

"We know you can't do that if you don't pass the test, but you can't be afraid to keep on going over the middle and doing what we've been doing."