Chelsea striker Diego Costa has discussed the idea of a return to former club Atletico Madrid and concluded: "You never know".

The 27-year-old Spain international has struggled to recapture his excellent first-season form for the Blues this term.

Costa's frustrations were laid bare at Tottenham almost a fortnight ago when he threw his substitutes bib at manager Jose Mourinho, after warming up in the second half but not taking to the field.

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He has since apologized for his actions, but Costa's start in the win over Porto on Wednesday was his first in three matches.

Asked about whether he could return to Atletico on Spanish radio stationOnda Cero, Costa said: "You never know.

"Look at how well Filipe Luis is doing. Life is full of surprises. I always wish Atletico the best and always follow them and support them from afar."

Brazil international Luis also struggled at Chelsea but returned to Spain in the summer in a £16m deal.

Costa moved from the Vicente Calderon to Stamford Bridge in a £32m deal in the summer of 2014 and scored 20 goals in 27 appearances in call competitions.

But as Chelsea have imploded in the Premier League, sitting 14th and 14 points short of the top-four following eight defeats in 15 games, Costa has found the net only four times in 19 games.