First off, not everyone can practice great, because for the most competitive people, having real competition lets them take it to another level that can't be simulated.
Secondly, let's decide that Bullock doesn't get hurt. They say that Mossad is tearing it up in practice, but yet it takes our top two RB's to get hurt for him to see a meaningful snap? We're not even running many two back sets to feature two backs that are "practicing well."
It's not that I doubt that Mossad eventually gets in, it's that I doubt that he becomes the starter or the feature back, when it is apparent to anyone watching that is exactly what he should be, and if he does, it is sometime in the next few weeks.
Look at Biels. Do you think a freshman is practicing better than Danny O'Brien? Do you think he has a better command of the offense, or is a better leader? Probably not, but he made the change.
I don't doubt Kirk is putting players out there that in his mind gives them the best chance, it's that I doubt he will actually bench a player that isn't getting it done.
And no where is it more apparent than at QB. Does James give us the best chance to win? Maybe he does, but he is also not winning. He is the QB - the captain of the offense and the single player most able to affect the game.
I realize I am coming from a place of ignorance, but I have a hard time believing that any of our other QB's could be worse.