http://www.sun-sentinel.com/sports/sfl-072608dolphinstrainingcampday1,0,6094177.story That Explains few things.
So in other words Porter probably feels like he doesnt need to start practicing this early... Thats my guess. It happens alot with Vets i'd think. Heck, look at the guys the pats have on their PUP list. Then again, who knows, maybe its a legit injury. However now news on it until now makes me feel a bit skeptical of it being legit.