They showed that if a bigger name comes knocking, you can sway their players to leave and they won't mind pushing a deal through. Gotze and Lewa, two players that Klopp developed into world class players were willing to dip for their biggest rivals as soon as they came knocking.
I'm not knocking Klopp nor Dortmund because I love what they are trying to do there but he reminds in someways of Wenger, for some odd reason or another his big players that he develops leave him. Unfortunately it comes down to finances, Wenger doesn't buy and sells because he's...well Wenger, and even he splashes for the occasional Sanchez but Klopp doesn't even have the warchest he does. Dortmund's overall club model is great but extremely difficult to maintain because of how limited their resources are.
It forces Klopp to continually have to make shrewd investments and develop his players from a certain level and bring them to the European stage. That's really hard to continually do by making moves low key moves during the window and without having a youth development program like we or Arsenal do. Klopp constantly has to scout foreign talent, integrate them into the squad and hope they perform in a short amount of time in what is a very demanding playing style. Sometimes it works but sometimes you fall a little short and when you're best players are getting offers to play with stars, its too hard to keep them unless you can bring in stars yourself and he can't. He can only bring in diamonds in the rough and I greatly admire him for this, but in someways can't you see how he sets himself up to fail? Without having a team of absolute stars on your squad, it is extremely difficult to compete at the highest level nowadays because of how inflated prices are now.
Don't forget about Kagawa nor Sahin either. They were both very important players to when they won Bundesliga and beat Bayern and they left as well for greener pastures. That's why, especially with how amazing he was for Germany this summer, it doesn't make sense why we aren't at least testing the waters for Hummels.
But nah, Vermalen will be greaatttt........