The 23-year-old joined the Bundesliga club last season on a season-long loan deal and featured 13 times but suffered a leg injury in January during the Africa Cup of Nations group opener against Uganda which ruled him out of the rest of the season.
He has since returned to Chelsea's training centre in Cobham to recuperate and started ball works last month, according to reports.
The German club's top hierarchy are hoping to have him back on loan.
"We are in talks with the player, his agent and Chelsea," Heidel told Schalke's official website.
"Ultimately, it is about when Baba Rahman will be able to play again. No decision has been made yet," he added.