Atletico Madrid's bid to re-sign Filipe Luis from Chelsea this summer reportedly hinges on the future of current left-back Guilherme Siqueira.
The Spanish outfit are in advanced talks with the Blues over a return for the Brazilian, who struggled to make his mark in England last season.
According to AS, a deal in the region of £11m has now been agreed between the two clubs, but Atletico must first find a new home for Siqueira.
Siqueira joined Atletico as Luis's replacement last summer, but it is understood that Diego Simeone's side cannot afford to have both players at the Vicente Calderon due to the restraints of FFP.
Luis, who has been offered a three-year deal by his former club, played a key role in Atletico's 2013-14 La Liga title success.