Grujic has spent the last two seasons on loan in Germany at Hertha Berlin, making an impact in the Bundesliga and sending his stock in Germany rocketing.
He could leave Liverpool before the transfer window closes on Monday night, with West Ham credited with an interest in landing him.
A return to Hertha Berlin can also not be ruled out and Preetz has indicated any move comes down to what Liverpool are looking for.
The sporting director told Sky Deutschland: “It is clear that we have contact.
“He was with us for two years.
“As with many other topics, it is also a question of the details here.”
Grujic made a total of 54 appearances for Hertha Berlin over the course of his loan spell and has played twice for Liverpool this season, in the EFL Cup.
The Serbian faces a tough task pushing into Liverpool’s midfield and the Reds are prepared to offload him if the offer on the table matches their expectations for the first player Jurgen Klopp signed as Reds boss.
