I'm shocked that Borussia Dortmund has not offered Mats Hummels a new contract, even though it is a one-year contract. Mats Hummels delivered a good performance against Real Madrid in the UEFA Champions League finals. Because of Mats Hummels, Real Madrid could not score so many goals against Borussia Dortmund. From what Mats Hummels displayed against Real Madrid, he still has a lot of things to offer as a defender. If it is certain that Borussia Dortmund wants to part ways with Mats Hummels this season, he will get a new contract with another club since he is on a free transfer.
As far as I've heard from the media, Hummels also no longer wanted to stay at Dortmund. There were apparently problems between Terzic and Hummels, but at 35 he probably wouldn't be able to be in the starting eleven.
Nuri Sahin is now taking over the head coach position instead of Terzic, which will also be a big challenge for him. They need to make a few good transfers this summer, because Reus and Hummels were important players who are no longer there.