Costa has been an influential figure in the Chelsea squad since his £35million switch from Vicente Calderon in 2014. The Spanish striker has helped the Blues win two Premier League titles and a League cup.
His future at the club, however, has been in doubt all summer after manager Antonio Conte made it clear that Costa is no longer in his first-team plans.
The 28-year-old is pushing for a move back to his former club Atletico Madrid, but has also been linked with a move to AC Milan and the Chinese Super League.
Simeone has remained coy over his plans to sign his former talisman. The Argentine manager, speaking after his sides 3-2 win over Premier League new boys Brighton, said, 'I don't want to comment too much'.
'The fact is he is still with Chelsea. The most important thing to me is the work of my club in general, not only in training. I have to work with what I have.'
'When I found there was no other possibility to get new players at the club I accepted it.'
'Maybe I could improve the quality, but for the moment with this team I can work very well and I'm satisfied with that.'
Atletico are currently shackled by a player registration ban imposed by FIFA. If the Spanish side were to sign Costa, he would not be able to play for the club until the ban is lifted at the start of next year.