Yup. As someone mentioned first in the thread, he's a rookie. There's a lot that comes from being a rookie. Moving to a new place, becoming a real professional at a young age, getting your own place to live, dealing with all the hanger-ons, working with agents and promotional stuff, dealing with your finances, learning to have fun and be responsible at the same time, etc...
This is before you even get into things like everyone around you is a lot better than in college, the fierceness of the competition, a playbook that is beyond what you're used to, the scrutiny of your play/performance by the media, the fact that you have to work a lot harder at your craft than before, etc, etc..
If a rookie comes in and hits the ground running from the start, that's exceptional. For some, it just takes time to adjust. A lot of life is being thrown at these guys. And fast. We sometimes forget this fact.