Union Berlin boss Oliver Ruhnert has described Robin Gosens as a "very interesting" player.
"He is a player who has played in the Champions League final. He's a player who is certainly very interesting for us. But there are a few of them. We play in the Champions League, but we are not a Champions League club," Ruhnert told Bild.
"We have a few ideas besides Gosens. But he is a very interesting player, no doubt about it."
According to reports, Union Berlin are looking into the possibility of bringing Gosens to Germany on loan with an obligation to buy.
VfL Wolfsburg are also said to be interested in the left-back.