Schalke signed goalkeeper Ralf Faehrmann from relegated German league side Eintracht Frankfurt at the end of the season, but Heldt insists the new shot-stopper is not guaranteed to be first-choice next season.
"We have always communicated that we would probably get a second new goalkeeper if Manuel Neuer leaves us," Schalke's director of sport Horst Heldt told Sport Bild online. "We have played through many scenarios and we have talked about Jens Lehmann."
Lehmann spent a decade at Schalke, from 1988 to 1998, and he worked with Heldt when the pair were both at Stuttgart, but the Schalke boss stressed things are still at the preliminary stage. "Jens has had some inquiries and he also basically needs to decide whether he will play on or not," said Heldt.
Lehmann, who turns 42 in November, completed his coaching licence at the end of May and signed a short-term contract with former club Arsenal to help them out of an injury crisis. He ended up playing a single Premier League match for the Gunners in April, having spent five years at the north London club from 2003 until 2008 when he moved back to Stuttgart before retiring in 2010.