Diego Costa has scored 21 goals in 36 matches in La Liga while he has also been highly impressive in the Champions League.
While Real Madrid and Paris Saint-Germain have been linked to Costa, Chelsea believes they are the frontrunners.
Chelsea are thought to value Costa at £27million – an amount below his release clause, but a fee that could be accepted if the player pushes for a switch away.
Atlético Madrid may want to replace Costa with Romelu Lukaku.
Lukaku is just 20 and Chelsea hasn't been able to find time for him on their roster. Lukaku spent last season with West Bromwich Albion and with Everton this season.
A deal involving Costa going to Chelsea for cash and Lukaku could materialize.
