The veteran hooker, who has played 208 NRL games across an 11-year career, doesn't have a contract for 2022 at this stage.
The Parramatta Eels are rumoured to be interested in the rake though according to an Courier Mail report, having lost their own backup this off-season.
With Joey Lussick signing in England, it means the Eels only options within their squad right now to back-up Reed Mahoney are Will Smith and Ray Stone, who performed admirably during the finals, but is a lock and cost Parramatta dearly at the back end of their semi-final against the Penrith Panthers.
Lussick played plenty of games this season for the Eels before suffering his own injury, with Mahoney struggling to stay fit at times.
Rein made 20 appearances this year for the Titans and can still perform at the top level, scoring two tries, assisting another and providing reliable service to his side.
It's understood Rein has already met with the Eels' coaching staff ahead of a potential move back to Sydney, where he played for both the St George Illawarra Dragons and Gold Coast Titans ahead of his move to the Gold Coast.
The Wollongong-born 31-year-old would be a cut-price signing for the Eels, who are also dealing with news today that Reed Mahoney will be a target for the 17th franchise when expansion is announced by the NRL within the next month.
The star hooker, who was due to make a Queensland debut before being derailed by injury this year, would return to his home state if he were to link up with the 17th club, and like a host of other Parramatta stars, is off-contract at the end of 2022, allowing him to negotiate from November 1.