The Saints have signed Angus Gunn from Manchester City for an initial £10 million, and it will inevitably push the England international down the pecking order behind Gunn and Alex McCarthy.
The 30-year-old wants to play regular first team football, and Southampton are keen to shift him away.
It will see them getting his wages off their books as Forster is one of the club’s top earners after signing a new five-year contract last summer.
With his future up in the air, there will be no shortage of clubs wanting to sign him, albeit temporarily.
Celtic fans have taken to social networking site Twitter to discuss the possibility of signing him again.
Forster was a massive success at Celtic (both in his loan and permanent spell) and left the club on good terms in 2014 for a fee in the region of £10 million.
He made over 190 appearances for the Bhoys and won three Scottish Premiership titles and two domestic cups.
He is still a very good goalkeeper and would be a fantastic addition for Celtic. Here are some of the reactions from Celtic fans on Twitter:
Fraser forster back to celtic would be class
— Paul Schiavone (@Paul_Schiavone7) July 11, 2018
@CelticFC bring Fraser Forster Home ☹️?⚽
— شبكة جماهير سيلتيك (@Celtic_Ar) July 11, 2018
I dunno why Fraser Forster has suddenly been told to leave Southampton. He was tremendous for celtic
— Joseph (@josephduffy81) July 11, 2018
Forster back to Celtic?
— Josh (@Flook95) July 10, 2018
What’s going happen today big Fraser Chris? Back to Celtic on loan? ?
— patrick o’hagan (@patohagan3) July 10, 2018
What’s happening with Forster. Now 3 0 to Celtic Chris
— Jim Cunningham (@JimCunningham4) July 10, 2018