The left-back spent last season on loan with German side Schalke, making 21 appearances before suffering a season-ending cruciate ligament injury.
However, following a hard debut campaign during which he started just 11 Premier League matches, Rahman was sent out on loan to German outfit Schalke 04 at the beginning of last season.
And, as confirmed by Schalke this afternoon, Rahman could be set for yet another loan spell at the Veltins-Arena this coming season.
"We are in talks with the player, his agent and Chelsea", Heidel said.
"Ultimately, it is about when Baba will be able to play again. No decision has been made yet".
The Ghana worldwide made 21 appearances for the Bundesliga side last term before he sustained a season-ending knee injury on global duty in January.
"I do not know what will happen tomorrow, the day after or next week".
Rahman's present deal with the Blues expires in June 2020 and there's indication he's not part of manager Antonio Conte's plans with Heidel hopeful of a reunion.
Rahman has made 23 appearances for Chelsea in all competitions since joining from Augsburg in 2015.