The Blues have made snapping up a top class centre-forward their priority ahead of the summer, with Jose Mourinho having been frustrated by his current crop of goal-getters all season.
Costa was mooted as a January target, but deals for Mohamed Salah, Kurt Zouma and Nemanja Matic took preference in a busy month.
However, Mourinho has not forgotten about the Brazilian-born forward, and is ready to make a big offer in six months’ time.
Costa is thought to be valued at around £35m, yet Chelsea are hopeful that they can reduce this figure to £20m by offering Atletico their former captain in exchange.
Torres came through the ranks at the Vicente Calderon before skippering the side and rising to prominence early in his career.
Despite leaving to sign for Liverpool, the much-maligned front-man is still thought of highly at his first club, which could tempt them to bring him back.
Torres was once one of English football’s most feared strikers, but his formed has dipped dramatically following his £50m switch from Anfield to Stamford Bridge in 2011.
Chelsea are also said to be tracking Luis Suarez, Edinson Cavani and Mario Mandzukic, while Wayne Rooney may also be a target after a number of failed bids last year.