The Hamburg sporting director is determined to keep the South Korean star at the Imtech Arena, but the player is remaining coy over signing a new deal with the club
The South Korean star has made an excellent start to the current Bundesliga season, and the Dane is determined to hold on to the player.
"He is a real poacher. Chance, boom, goal," the 56-year-old told Hamburger Abendblatt.
"He is one of our key players for the future. Our pain barrier concerning Son is gigantic. We do not want to give away players who make us better, under no circumstances."
However, the player is reluctant to commit his future to the club, but stressed that he was enjoying his time at the Imtech Arena.
"[I feel] very, very comfortable [at Hamburg]. The City is amazing and the fans are really terrific," he raved.
"I still have a contract until 2014 and I have to talk about it with my dad and my agent."