There is a difference, albeit a subtle one, between what we'll define as "breaking out" and what we'll define as "exploding."
A breakout player is one who goes from relative obscurity to relative renown. They post stats few people expected given how they performed the season (or seasons) before.
A player we'll deem "set to explode" is one who ended last season on the verge of something. Even if they're already well known—which many players on this list are—the stars (and depth charts) might be aligning for them to reach new heights in 2014.
In this regard, a breakout player is a subcategory of an exploding player. It's the same relationship as that of a square to a rectangle. If a player breaks out, he has exploded; but if a player explodes, he hasn't necessarily broken out. The breakout may have previously happened.
This list includes many types of set-to-explode players. There are breakout candidates who are set to start full-time duty for the first time. There are former All-Conference players who might make the leap to All-America. There are different types of players in between.
But each is in store for a potentially huge season.