This first article by Vic Carucci I think gets to the heart of all of this:

The points you made about the deficiencies of Young's game are valid, but I'm actually less concerned about them than I am about his psyche. Through coaching and by applying himself in practice and the meeting room, Young can improve those technical shortcomings. The question is, does he want to? Does he have the desire to make the commitment to improve his game? Does he truly enjoy being an NFL quarterback enough to do the things that are necessary to get the most out of his skills?

The second article has some interesting insight from players and coaches, good stuff about Collins and the adversity he's faced, too (emphasis mine):

But one of his teammates, requesting anonymity, said: "Vince is frustrated, and we understand that. Who wouldn't be? He is used to being on the big stage. He is used to being the man. It's pride. I think he believes he is that guy from Texas and that he is beyond some things. He expects to perform at a high level all of the time. But now he is dealing with injury and failure in the fans' eyes. He's still a winner. He can still be our guy. It won't help if he mopes around now. And we've got to keep reaching out to him and let him know that we are still behind him."

...

"It is a major change, what we are asking him to do," Heimerdinger said. "He has always been the best athlete on the field. He has always had the special ability to run like few can run when things are not there. When hurt, he can't run and move at will. There is a reluctance to go. It's a gamble. Then that ability that helps him make plays running and passing (that) others can't isn't there. I felt every week before he got hurt, he was growing. If everybody is patient enough, he will be fine. But I must say, he is a player where there doesn't seem to be a lot of patience with him on the outside. For some reason, it's just that way. And that is hard to figure."

I keep hearing that Vince first needs to win the locker room back.  Aside from Bullock's comment (which wasn't direct), I haven't read anything that indicates he ever lost it.  I've yet to watch/read/hear anything that leads me to believe that VY won't start for the Titans again in the future.