How Brad Stevens transformed from a college basketball assistant making $18,000 a year to one of the best coaches in the NBA

Maddie Meyer/GettyOver the course of four years, Brad Stevens has helped transform the Boston Celtics from a lottery team to a title contender.

The turnaround has been stunning - the Celtics lack any traditional stars, and when they hired Stevens from Butler, they were supposed to be tanking.

Instead, Stevens has built a system of selfless, motion basketball that has turned a 5-foot-9 point guard in Isaiah Thomas into a dynamic scorer and turned a team of role players into one solid unit.

The NBA world has taken notice, as a former assistant-turned-head coach in college is beating NBA coaches at a level nobody expected.

Here's how Stevens has risen from an assistant making $18,000 a year collecting film to one of the best coaches in the pros.