The German is already training with the Potters this week.
"I like the look of him," says Hughes. "He's has a good presence and is technically a good player.
"He's played at a high level, and big money has been paid for him. He's still a young man with his future very much ahead of him.
"I've met him and he's very excited and very keen to come over here and make an impact. To get a good, young German defender is a great boost for us."