His biggest limiting factor is his attitude. Pass protection is about willingness more than anything else. We can go find lots of links, but living here his story is old and tired.
He's constantly late to practice ($15K+ in fines), even to the point the team hired a car service to get him there. He's lazy and is wasting what has shown to be NFL caliber talent. When he's motivated and puts in the work, he sees the field and does what he's good at - run with the football, over and around people.
His attitude is the one constant in everything you read about him - if he gets his head on straight, I think he has a chance to be a solid contributor. He started to say the right things last year instead of complaining, so maybe it took a hard-liner like Schiano to get him sorted out. Here's a quote from October:
"At the end of the day, if they tell me to go in, I'm going to be ready," Blount told Stephen Holder from the Tampa Bay Times. "I might not play as much, but I stand there and listen and do everything that everybody else does. My time will come. And I'll be ready."