Let's be honest: The Denver Broncos know what most of the depth chart is going to look like already, so training camp battles are mostly for depth. This is one team where the top-end positions are pretty much decided. Even the new guys—DeMarcus Ware, T.J. Ward, Aqib Talib, Emmanuel Sanders—know where they stand. They'll all start.
That being said, depth is huge in the NFL, and it often wins games—and even Super Bowls. The injuries that hindered Denver late in last season—Ryan Clady, Chris Harris, etc.—could have been better overcome with more depth. It's also important for the long-term future of the team, something that is always a bit in flux.
On top of that, the NFL is changing. A third cornerback used to be considered a second-string player. With the amount of nickel coverage that has to be run these days, that guy is pretty much a starter. He needs to be able to play like it. The same can be said for a backup safety if the starter is going to be brought up into the box and used like a linebacker at times, as the Broncos may do with Ward.
With training camp finally underway, the last pieces of the puzzle can start to fall into place. These battles are simply ranked according to their importance to the team's immediate future, mostly based on playing time.