The terms "breakout player" and "most-improved player" are often confused with one another, which is understandable. They're pretty similar, but they aren't necessarily the same thing.
Breakouts come out of relative obscurity, making a name for themselves where there probably wasn't one before. They are unexpected contributors that have a big impact.
The Pac-12's most-improved players don't have to also be breakouts. In fact, they usually aren't. Generally, they are better-known commodities and players familiar to more than just conference diehards.
They just happen to take a quantum leap forward from one season to the next.