Hummels returns to Dortmund: a perfect fit that could unsettle Bayern

Hummels still has plenty left to offer in a top club's defense but will Bayern regret letting him leave so easily for their biggest and strongest rival?

Why? The obvious and indeed most accurate answer is that all three parties felt that Mats Hummels' move back to Borussia Dortmund from FC Bayern Munich was in their interest. But that tells us nothing about how each of them arrived here, and then quickly found an agreement that would have seemed beyond the realm of fantasy a few months ago.

Borussia's thought process is relatively easy to explain. The main reason that last season's runners-up failed to win the league was their young defence's...