The Brazilian-born La Roja international joined the Blues last year from Atletico Madrid and immediately helped the London club to Premier League glory with 20 goals across the campaign.
He’s contribution was lauded by fans and pundits alike, with some suggesting that he’d filled the boots of Stamford Bridge idol Didier Drogba, who was the main man up front during the club’s successes through the mid to late 2000s.
However, this season has been far less fruitful for Costa, whose performances and divisive playing style have been roundly criticised.
The 27-year-old has netted just twice in league action, and reports claim that he’s eager to head back to Spain, with a return to Madrid his favoured option.
He registered 36 goals in all competitions for Atletico during 2013/14, as they won La Liga and reached the Champions League Final.
Interested from either Atleti or Real Madrid has not been mooted, but Barcelona are thought to be keen.