As exclusively revealed by Goal.com on Thursday, the 22-year-old has decided against renewing his current contract, which expires in the summer, after failing to reach an agreement with the Bundesliga outfit.
He has been linked with a number of European clubs, including Bayern Munich and Liverpool, but his agent denied that Holtby has been approached by the Bavarians.
"The reports [of Holtby being targeted by Bayern] surprised me," Noack told TZ.
"There is no truth to this rumour, it's just speculation."
Holtby has become a key player at the Veltins Arena after a brief period of adaptation following his successful loan spell at Mainz in the 2010/11 season.
The midfielder, whose current deal with the Gelsenkirchen outfit expires in 2013, has netted three times and provided five assists in 17 Bundesliga appearances for the Konigsblauen so far this season.