Chelsea will have to pay £14m if they are to sign Toby Alderweireld, according to Daily Telegraph.
Current Blues defender Filipe Luis is keen to return to Spanish football with Atletico Madrid after failing to make his mark on English football, settling for a place on the bench at Stamford Bridge.
His proposed summer exit will leave Blues boss Jose Mourinho short on defensiveoptions, but it is understood that the Portuguese coach has looked into the possibility of signing Saints defender Alderweireld.
The 26-year-old defender has enjoyed a solid first season in the Premier League on loan at Southampton from Atletico Madrid.
As a result, Ronald Koeman’s side do have an option to make the loan permanent for £6.8m, while the Spanish club can buy out the rest of the loan for £1.5m to sell their man to the highest bidder.
The defender is rated at £11m but a clause in his contract means Atletico Madrid must pay Southampton £3m if he goes elsewhere.