A club that has never been among Europe's top handful of rich sides, Borussia Dortmund have had somewhat of a revolving door of star players in recent years.
Shortly after winning the Bundesliga in 2011 and 2012, Nuri Sahin and Shinji Kagawa, respectively, were sold and later replaced by Ilkay Gundogan and Marco Reus.
Mario Gotze left the club in 2013, and Robert Lewandowski in 2014, with the pair replaced by Henrikh Mkhitaryan and Pierre-Emerick Aubameyang, respectively.
Now Gundogan and Mkhitaryan have left this summer—along with Mats Hummels—and the club will look to figure out the best possible replacements for each.