Fraser Forster will move to Southampton if Celtic crash out of the Champions League

The Celtic goalkeeper will be allowed to move south of the border provided his club fail to overturn their Champions League deficit tonight

Celtic will let Fraser Forster leave if they fail to progress in the Champions League (Reuters)

Fraser Forster will leave Celtic for Southampton this summer - provided the Hoops do not overturn a 4-1 deficit against Legia Warsaw in tonight's Champions League third qualifying round encounter at Murrayfield.

Southampton have agreed a fee with Celtic for the England international believed to be £8 million - almost double the Saints' initial bid of £4.5 million which was described as "derisory" by Celtic.

The Glasgow club face a monumental uphill task in holding onto Forster, however, requiring a 3-0 victory in Edinburgh this evening in order to progress and stand a chance of retaining their stopper, who travelled as part of the England squad to Brazil for the World Cup.

Koeman is also said to be keen on signing Forster's Celtic teammate Virgil van Dijk as he attempts to rebuild his squad following the loss of several key players.

However, his desire to sign Forster may signal the end of the Southampton road for Artur Boruc, who has been linked with a move to Bayern Munich.

The departures of Rickie Lambert, Luke Shaw, Adam Lallana, Dejan Lovren and Calum Chambers have been exacerbated in recent weeks by the unrest provoked by Tottenham Hotspur's pursuit of Morgan Schneiderlin and Jay Rodriguez.

Forster was selected for England's World Cup squad but did not play a game (Getty)

Koeman's desire to sign Forster may signal the end of the Southampton road for another former Celtic keeper in Artur Boruc, who has been linked with a move to Bayern Munich.