Bayer Leverkusen are a pain to do business with, as evidenced by the way they've dealt with Andre Schurrle over the past several seasons. They've reached an agreement with Chelsea over a fee for the German international, but don't want to allow him to depart without first acquiring an attacker to replace him.
If true, that would have serious repercussions for both clubs. Bayer would seemingly have an unhappy player going forward, as this would be two summers in a row in which he's had a move to one of Europe's elite fall through. For Chelsea, this would likely mean Kevin De Bruyne is less likely to head out on loan, or that Chelsea turn their attention to other targets in that area.
As many of you aren't all that fond of the potential Schurrle/De Bruyne deal anyway, I'm sure you'll be excited by this news. Who knows, this might even convince the German side to take Chelsea's money without the player and get their business done as soon as possible. At least it's sounding like this one will be done sooner rather than later, regardless of whether done means we end up with Schurrle or not.