The Blues insist Costa remains a vital member of their squad despite an indifferent season which has seen the Spaniard score just six league goals.
Atletico manager Diego Simeone clearly still rates the striker and with Jackson Martinez struggling to find his feet at the Vicente Calderon, bringing Costa back would be seen as a welcome addition.
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Both Simeone and Martinez are reported targets of Chelsea, who are on the lookout for a new manager alongside attacking reinforcements.
Costa has found life difficult in the Premier League this season - a stark contrast to the 27-year-old's dominance last season, when he scored 20 league goals.
The Brazil-born striker has often cut a frustrated figure in a side bereft of attacking potency, with Eden Hazard and Cesc Fabregas similarly struggling.
However, Guus Hiddink's side showed glimpses of their former best last weekend against Crystal Palace, claiming an impressive 3-0 win over the Eagles at Selhurst Park.
Costa played a vital role in the Blues' victory, assisting Oscar's opener and then tapping home from close range midway through the second half.
Simeone's interest in Costa could ultimately benefit Chelsea given the Argentine manager is linked with a move to west London this summer.
One of the favourites to take charge at Stamford Bridge, Simeone has a release clause of £8 million and could help his former player to rediscover the form that helped Atletico to the La Liga title in 2014.