The former Atletico Madrid man took to social media and posted an image of him and Costa with the same caption.
Costa is now believed to be consulting with his lawyers, while Chelsea claim that he must return to fulfil his contractual obligations.
He revealed his intention to return to Atletico but the move failed to materialise due to Chelsea's £50m demands.
Chelsea manager, Antonio Conte, is finding life a bit more hard in his second season at Stamford Bridge.
Jets trade Sheldon Richardson to Seahawks for veteran WR
I want to get out there and start on defense. "He should be embarrassed", Richardson said, per the New York Post . Kearse, a five-year veteran, had 41 catches for 510 yards last season with the Seahawks, but just one touchdown.
Diego Costa might be sued by Chelsea.
Meanwhile, Costa has been encouraged to return to fitness by Spain team-mate Sergio Ramos.
It is fair to say that they are in a mess with their tactics and they offer me the chance to score goals as they get confused.
"And now I find a team that has made a huge financial commitment for a Real Madrid substitute".
'You have to battle with the centre backs and physically they are a lot stronger than in any other league.
'Here if you hold on to the ball for too long they have already given you a couple of kicks'.