The 32-year-old spent the whole of 2019-20 on loan with the Scottish giants, returning for a second stint having spent four seasons with them between 2010 and 2014.
Celtic were keen to retain his services on loan for another season after he helped them win a ninth consecutive Scottish Premiership title, but Forster turned down the chance as he was keen to prove himself to Southampton manager Ralph Hasenhuttl.
However, he hasn’t been granted a regular first-team opportunity at St. Mary’s, and a permanent exit doesn’t appear to be on the cards with his deal not expiring until the summer of 2022.
While Celtic still feel slighted after Forster rejected the chance to return to Parkhead in the summer, both parties could do with each other given how the campaign has gone for both of them thus far.
Hoops manager Neil Lennon brought in Vasilis Barkas from AEK Athens, but the 26-year-old hasn’t been particularly impressed.
He is not solely responsible for their woeful Europa League campaign, neither is he the reason why they are 13 points behind Rangers with two games in hand.
However, many will argue that Celtic would have fared better thus far if they had Forster in goal.
The Southampton man currently earns £70,000-a-week, and the EPL side will be keen to let him go in January as he is clearly not in their plans.
He brings the needed experience and inspiration, and having him in goal could help improve Celtic’s fortunes for the second half of 2020-21.
Forster’s return could also help bring out the best in the struggling Barkas, and it will be interesting to see if the Hoops will go after his signature in January.
They will need to make quality additions to their squad next month if they want to get their title challenge back on track, and landing the Southampton man could come in handy.