For me, it's all about the best player available (BPA) that fills a need for your team. The only exception is QB because the NFL is a QB driven league and you need one to win it all. There are a few exceptions like when you have a dominating defense like Denver did.
Summary: Hummel battled through two horrific knee injuries to have a terrific senior season with the Boilermakers. He is by no means a typical NBA athlete, but his work ethic, heart, ability to shoot the ball and intangibles could land him a spot in the second round.
Player Comparison: Luke Babbit.
Babbit is a skilled forward who can shoot the ball from the outside, but his lack of athleticism has held him back in the NBA. Hummel figures to go through a similar struggle in transitioning to the next level.