The attacking midfielder has impressed in Germany this season and has had scouts watching him in action from England, Italy and Spain.
The 19-year-old has a contract with the Gelsenkirchen outfit until June 2016 and is currently valued in the £10million bracket, although that could rise if he continues to progress.
Heldt has revealed Inter, Chelsea and Manchester United are all tracking him, while Juventus are also credited with an interest.
"There are a lot of international level clubs that are following him," Heldt told Bild.
"We have seen them several times. We are talking about teams like Inter, Chelsea and Manchester United."