Here's a clip of him doing some drills back in 2009 as a Sr. in college. Look how small he was compared to how big he is now. This is also not just normal age gain that occurs as a young male fills out in his early 20s as he was already 22 here at the Ole Miss Pro Day in 2009:
http://www.youtube.com/watch?v=dYVIlj_-B_E
You an actually see them doing some pass drills with him as I think he was still a TE back then.
The one thing that is obvious from the video is how raw he was as a football player here. He definitely still looks like a basketball player and looks very awkward trying to do football drills out there.
My guess is at some point he realized he wasn't going to make it in basketball and someone noticed his great strength and figured he should give football a try.