Atletico Madrid have reportedly offered Chelsea the services of striker Jackson Martinez in exchange for Diego Costa.
The 29-year-old has struggled to adapt to life at the Vicente Calderon since his summer switch from Porto, leaving Atletico keen to offload him this month ahead of a possible ban on transfer activity this summer.
According to The Sun, Chelsea are "unlikely" to agree a deal in the next few days as any swap would leave both men ineligible to feature for their new clubs in the Champions League.
The newspaper claims that Costa is "in regular contact" with teammates at his former club and "pines" for a return to the Spanish capital.
Atletico are currently second in La Liga, level on points with leaders Barcelona.
