In August 2016, Rahman signed a season-long deal with the Bundesliga side before midway through the campaign, the Ghanaian international sustained a serious knee injury.
However, after a year on the sidelines, Rahman is close to a return to action and Heidel has revealed that the German outfit are keen to secure his services before the end of the month.
On Schalke 04's official Twitter page, Heidel is quoted as saying: "We're in talks with Chelsea regarding Baba Rahman. There are still one or two things to clear up on their end.
"We could agree on a deal with the player himself relatively quickly."