There is also something about the testing. I was never called brilliant, but I could take a test with the best of them. I was athletic when I was younger, but I would never be considered for a pro athlete. I'd be willing to think he might not be dumber than a tree stump, but might not be able to test very well. I've known several people like that in my lifetime: people who could converse on any number of topics in multiple languages, but could barely fill out an application.
Like what was said, there are few that are gifted both intellectually and athletically.