No reason, if BJ does a great job, that he can't move up the depth chart during the season.
Cousins first started week 14 ... I'd be fine having this conversation about Daniels over McCoy in 4 months. But TODAY ... I think McCoy gives the 49ers a better chance to win than Daniels does. McCoy will get better for a while then plateau, Daniels should have a much higher ceiling.
Maybe when Crabtree comes back McCoy is the roster spot he takes :)