Mourinho says he has been able to avoid rushing Costa back into action due to the substantial cushion his side hold at the top of the Premier League table – with the Blues looking to be crowned champions with three games to spare with a derby win on Sunday.
The Chelsea boss says his top scorer isn't worth risking in that contest, telling reporters he might not play for the rest of the season.
"If we win on Sunday, I would say he doesn't play against Liverpool. If we don't win on Sunday and we need points, I would say he plays against Liverpool."
The Chelsea manager was asked how he would celebrate when his side win the title, saying that he will 'go home', but has admitted that he wants his side to finish the job as quickly as possible.
“In this moment we have nothing prepared.
“Normally I will finish the game and go home.
"Obviously we want to finish as soon as possible. If we can do it at home, better.
"If we can do it on Sunday, even better. That's what we have in our minds. But similar to Arsenal, similar to Leicester, we go to win but at this moment any point we get is a positive point."
The subject of whether his side can win multiple titles cropped up, but Mourinho stressed that the Premier League is a very competitive division and suggested that the first objective for next season will be finishing inside the top four, with it important for his side to avoid any complacency as they seek to dominate English football.
He added: "This is a very competitive championship.
"It's not over yet. Everybody for sure works hard to try to reach their objectives."