Costa has been the standout player in Atletico's exceptional season to date, with his 26 goals in 31 Primera Division matches giving his side an excellent chance of winning their first league title since the 1995-96 campaign.
It is therefore unsurprising that the Brazil-born Spain international has attracted the attention of several leading European clubs, and Jose Mourinho's Blues are reportedly at the front of the queue.
It would take a substantial offer for Atletico to contemplate selling their prize asset although Simeone believes Costa will ultimately decide his own future.
"It depends on him and what he believes is best for his future. I will support any decision," the Argentinian told AS.
Costa will be hoping to showcase his talents against Chelsea in the Champions League semi-finals, a clash that has been made more intriguing by the prospect of the Blues' own goalkeeper turning out for Atletico.
Thibaut Courtois is on loan at Atletico for a third successive season and Chelsea insist he will be free to play against them, in line with UEFA rules, as the clubs compete for a place in the May 24 final in Lisbon against Real Madrid or defending champions Bayern Munich.
It was reported that Chelsea would allow the Spanish side to play the Belgian in both legs of the semi, provided they paid a fee of around 3million euros for each game.
However, UEFA moved to clarify that it expects Courtois to be free to face the Blues in both legs and Simeone has no doubt that the 21-year-old will be available for selection.
"I have no doubt that he will play against Chelsea. He also has no doubts. Not a concern," Simeone said.
There has been some suggestion Courtois could be used as a makeweight if Chelsea do pursue their interest in Costa, but Simeone does not know whether the Belgian's future lies at the Vicente Calderon.
"It is not yet know where he will play next year," he added.
- Sports & Recreation
- Diego Costa
- Jose Mourinho