Welsh was wanted by French side Toulouse in the last summer transfer window, but Celtic rebuffed interest, with Postecoglou not wanting to lose the central defender.
However, the Bhoys have now shifted their stance on Welsh, despite the fact that Postecoglou remains a firm admirer of his abilities.
It is suggested that Postecoglou understands Welsh’s desire to be playing on a regular basis and as such, will sanction an exit.
Celtic are now open to offers for the 22-year-old.
Welsh is already attracting interest from clubs in Europe and the MLS, though it remains to be seen if any of the interested parties will be able to reach an agreement with Celtic.
Celtic have already added to their centre-back options during this month’s transfer window.
The Hoops snapped up Japanese defender Yuki Kobayashi from Vissel Kobe, with the 22-year-old putting pen to paper to a five-year deal at Parkhead.
