Sunderland must fork out £7million to land Olympiakos full-back Arthur Masuaku in January.
The Greek side have slapped the hefty transfer fee on their highly-sought after French left-back, who is being courted by several European big-hitters.
The Black Cats are seriously weighing up a move for the 22-year-old when the window opens and club scouts have watched Masuaku in action three times.
Masuaku has impressed this season and sources in Greece say the highly-rated youngster has proved he can play at the highest level after starring in their Champions League campaign.
The £7million - or 10million Euros - fee would be a big outlay but Allardyce is desperate to shore up his leaky defence.
Masuaku – who joined Olympiakos from French side Valenciennes 18 months ago – is a former France Under-19 international and is tipped to soon be called into the full squad, ahead of Euro 2016.
Sunderland scouts last watched him in action during the Greek club’s Champions League win over Dynamo Zagreb last week and he is one of several names on the shortlist drawn up by Allardyce & Co.
They would face fierce competition to land his signature though, with Serie A heavyweights Inter, Juventus and Roma all scouting him over recent months.
Roma were in talks over a possible transfer in the summer, but sources in Greece have indicated that Sunderland are keen on a January deal for Masuaku, who is under contract at Olympiakos until the summer of 2018.
Patrick van Aanholt is the only specialist left-back in Sunderland’s squad, but the Dutchman has made just one start under Allardyce in a more advanced wing-back position. He has been struggling for form this season.
Despite Sunderland making eight signings during the summer, Allardyce wants fresh blood in January, players who can make an immediate impact on the first team.
And Allardyce has also been linked with a fresh move for one of his old boys at West Ham United - experienced Welsh centre-back James Collins.
Strengthening the defence is key and several players could be moved on to help fund the January spending including Danny Graham, Adam Matthews, Seb Larsson and Liam Bridcutt.
Bridcutt’s proposed loan move to Leeds is still in the pipeline but face competition from Championship rivals Cardiff City and Reading.
Emmanuele Giaccherini has already gone out on loan, and is making an impression at Bologna, where he has scored twice in six games this season.
However, his agent, Furio Valcareggi, told Radio Nettuno: “Giaccherini is happy in Bologna but in June he will be going back to Sunderland.
“He has another year of his contract left with the Black Cats, and after then we will see.”
Sunderland’s battle against relegation looks increasingly bleak after the 1-0 defeat to Ronald Koeman’s Saints at the Stadium of Light.
Defeat leaving the Black Cats four points adrift from safety.