Chelsea manager Jose Mourinho says Felipe Luis is poised to leave Stamford Bridge, a move that will prompt the Blues into signing another left-back.
Luis, 28, was part of the Atletico Madrid side that shattered Barcelona and Real Madrid's monopoly on the Spanish title in 2014, and he has been heavily linked with a return to the Vicente Calderon in recent weeks.
The Brazil international was unable to displace Cesar Azpilicueta at left-back following his arrival at Chelsea and made just 15 appearances for the Blues in the 2014-15 season.
Mourinho has already indicated he is ready to allow the player to return to Madrid, with Spanish newspaper Marca suggesting a fee of €16m (£11.1m, $17.3m) is already in place.
Speaking at a press conference in Montreal as part of the club's pre-season tour, the Chelsea boss said the club are likely to need a replacement as Filipe Luis is on the verge of being sold, as reported via the club's official Twitter account.
Atletico Madrid manager Diego Simeone indicated to Spanish daily AS in June he was ready to welcome Filipe Luis back to the Vicente Calderon with open arms, with the defender's former teammate Koke reassuring him he will not be looked upon as a traitor after leaving the club last summer.
"Filipe Luis decided to leave and now he has the chance to return," Koko told Marca.
"If he arrives, there will be more competition, and that's good. We'll be a better team and fight for more things. He is no traitor. As long as he plays and plays well there won't be any problem."
Chelsea will look into bringing Augsburg left-back Baba Rahman to Stamford Bridge as a replacement, according to the Daily Mail, who add the 21-year-old Ghana international will cost £15m.