Southampton are confident they have a £25million-plus asset on their hands following Fraser Forster’s stunning rejuvenation at Celtic, Football Insider understands.

The goalkeeper, 31, has reignited his career during his second spell at Parkhead after being frozen out for 18 months at the Premier League outfit.

A Southampton source has told Football Insider the club are keeping close tabs on Forster and are expected to sell him on at a profit next summer.

A permanent move to Celtic is unlikely as his Saints contract is worth £70,000-a-week and runs until 2022.

Nevertheless, the 6ft 7in giant is likely to have plenty of interest from Premier League clubs at the end of the season, especially if he continues his current outstanding form.

Forster almost singlehandedly denied Rangers in yesterday’s Scottish League Cup final with a man-of-the-match performance that included a penalty save and a series of other outstanding stops to secure a 1-0 triumph for Neil Lennon’s side.

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The goalkeeper could return to Southampton but he was behind Angus Gunn and Alex McCarthy in the club’s keeper pecking order before he went out on loan in August and had spent 18 months in the wilderness.

He is unlikely to want to stay at St Mary’s Stadium unless he is the number one, a position currently held by McCarthy, 30, while the club have high hopes for Gunn, 23.

Forster has made 20 appearances for the Hoops since his return, keeping eight clean sheets and conceding just 13 goals.

His grip on the number one jersey is set to face strong competition from Scott Bain, who is close to recovering from a dislocated figure sustained in August.

In other Celtic news, it can be REVEALED that Nicky Hammond has laid down law to £10m+ valued Hoops star in transfer showdown.